Date API Flashcards

Question 1

Q

Date() constructor

Answer

A

The Date() constructor creates Date objects. When called as a function, it returns a string representing the current time.

Syntax

new Date()
new Date(value)
new Date(dateString)
new Date(dateObject)

new Date(year, monthIndex)
new Date(year, monthIndex, day)
new Date(year, monthIndex, day, hours)
new Date(year, monthIndex, day, hours, minutes)
new Date(year, monthIndex, day, hours, minutes, seconds)
new Date(year, monthIndex, day, hours, minutes, seconds, milliseconds)

Date()

Note: Date() can be called with or without new, but with different effects.

Parameters

There are five basic forms for the Date() constructor:

No parameters

When no parameters are provided, the newly-created Date object represents the current date and time as of the time of instantiation. The returned date’s timestamp is the same as the number returned by Date.now().

Time value or timestamp number

value - An integer value representing the timestamp (the number of milliseconds since midnight at the beginning of January 1, 1970, UTC — a.k.a. the epoch).

Date string

dateString - A string value representing a date, parsed and interpreted using the same algorithm implemented by Date.parse(). See date time string format for caveats on using different formats.

Date object

dateObject - An existing Date object. This effectively makes a copy of the existing Date object with the same date and time. This is equivalent to new Date(dateObject.valueOf()), except the valueOf() method is not called.

When one parameter is passed to the Date() constructor, Date instances are specially treated. All other values are converted to primitives. If the result is a string, it will be parsed as a date string. Otherwise, the resulting primitive is further coerced to a number and treated as a timestamp.

Individual date and time component values

Given at least a year and month, this form of Date() returns a Date object whose component values (year, month, day, hour, minute, second, and millisecond) all come from the following parameters. Any missing fields are given the lowest possible value (1 for day and 0 for every other component). The parameter values are all evaluated against the local time zone, rather than UTC. Date.UTC() accepts similar parameters but interprets the components as UTC and returns a timestamp.

If any parameter overflows its defined bounds, it “carries over”. For example, if a monthIndex greater than 11 is passed in, those months will cause the year to increment; if a minutes greater than 59 is passed in, hours will increment accordingly, etc. Therefore, new Date(1990, 12, 1) will return January 1st, 1991; new Date(2020, 5, 19, 25, 65) will return 2:05 A.M. June 20th, 2020.

Similarly, if any parameter underflows, it “borrows” from the higher positions. For example, new Date(2020, 5, 0) will return May 31st, 2020.

year - Integer value representing the year. Values from 0 to 99 map to the years 1900 to 1999. All other values are the actual year. See the example.
monthIndex - Integer value representing the month, beginning with 0 for January to 11 for December.
day Optional - Integer value representing the day of the month. Defaults to 1.
hours Optional - Integer value between 0 and 23 representing the hour of the day. Defaults to 0.
minutes Optional - Integer value representing the minute segment of a time. Defaults to 0.
seconds Optional - Integer value representing the second segment of a time. Defaults to 0.
milliseconds Optional - Integer value representing the millisecond segment of a time. Defaults to 0.

Return value

Calling new Date() (the Date() constructor) returns a Date object. If called with an invalid date string, or if the date to be constructed will have a timestamp less than -8,640,000,000,000,000 or greater than 8,640,000,000,000,000 milliseconds, it returns an invalid date (a Date object whose toString() method returns "Invalid Date" and valueOf() method returns NaN).

Calling the Date() function (without the new keyword) returns a string representation of the current date and time, exactly as new Date().toString() does. Any arguments given in a Date() function call (without the new keyword) are ignored; regardless of whether it’s called with an invalid date string — or even called with any arbitrary object or other primitive as an argument — it always returns a string representation of the current date and time.

“Date() constructor - JavaScript | MDN” (MDN Web Docs). Retrieved March 14, 2024.

Question 2

Q

Date.prototype[@@toPrimitive]()

Answer

A

The [@@toPrimitive]() method of Date instances returns a primitive value representing this date. It may either be a string or a number, depending on the hint given.

The [@@toPrimitive]() method is part of the type coercion protocol. JavaScript always calls the [@@toPrimitive]() method in priority to convert an object to a primitive value. You rarely need to invoke the [@@toPrimitive]() method yourself; JavaScript automatically invokes it when encountering an object where a primitive value is expected.

Syntax

date[Symbol.toPrimitive](hint)

Parameters

hint - A string representing the type of the primitive value to return. The following values are valid:

"string" or "default": The method should return a string.
"number": The method should return a number.
Return value

If hint is "string" or "default", this method returns a string by coercing the this value to a string (first trying toString() then trying valueOf()).

If hint is "number", this method returns a number by coercing the this value to a number (first trying valueOf() then trying toString()).

Exceptions

TypeError - Thrown if the hint argument is not one of the three valid values.

Examples:

const d = new Date(0); // 1970-01-01T00:00:00.000Z

d[Symbol.toPrimitive]("string"); // "Thu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)"
d[Symbol.toPrimitive]("number"); // 0
d[Symbol.toPrimitive]("default"); // "Thu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)"

“Date.prototype[@@toPrimitive]() - JavaScript | MDN” (MDN Web Docs). Retrieved March 20, 2024.

Question 3

Q

Date.prototype.getDate()

Answer

A

The getDate() method of Date instances returns the day of the month for this date according to local time.

Syntax

getDate()

Parameters
None.

Return value
An integer, between 1 and 31, representing the day of the month for the given date according to local time. Returns NaN if the date is invalid.

Examples:

const xmas95 = new Date("1995-12-25T23:15:30");
const day = xmas95.getDate();

console.log(day); // 25

“Date.prototype.getDate() - JavaScript | MDN” (MDN Web Docs). Retrieved March 20, 2024.

Question 4

Q

Date.prototype.getDay()

Answer

A

The getDay() method of Date instances returns the day of the week for this date according to local time, where 0 represents Sunday. For the day of the month, see Date.prototype.getDate().

Syntax

getDay()

Parameters
None.

Return value
An integer, between 0 and 6, representing the day of the week for the given date according to local time: 0 for Sunday, 1 for Monday, 2 for Tuesday, and so on. Returns NaN if the date is invalid.

Description
The return value of getDay() is zero-based, which is useful for indexing into arrays of days, for example:

const valentines = new Date("1995-02-14");
const day = valentines.getDay();
const dayNames = ["Sunday", "Monday", "Tuesday" /* , … */];

console.log(dayNames[day]); // "Monday"

However, for the purpose of internationalization, you should prefer using Intl.DateTimeFormat with the options parameter instead.

const options = { weekday: "long" };
console.log(new Intl.DateTimeFormat("en-US", options).format(valentines));
// "Monday"
console.log(new Intl.DateTimeFormat("de-DE", options).format(valentines));
// "Montag"

Examples:

const xmas95 = new Date("1995-12-25T23:15:30");
const weekday = xmas95.getDay();

console.log(weekday); // 1

“Date.prototype.getDay() - JavaScript | MDN” (MDN Web Docs). Retrieved March 20, 2024.

Question 5

Q

Date.prototype.getFullYear()

Answer

A

The getFullYear() method of Date instances returns the year for this date according to local time.

Unlike getYear(), the value returned by getFullYear() is an absolute number. For dates between the years 1000 and 9999, getFullYear() returns a four-digit number, for example, 1995. Use this function to make sure a year is compliant with years after 2000.

Syntax

getFullYear()

Parameters
None.

Return value
An integer representing the year for the given date according to local time. Returns NaN if the date is invalid.

Examples:

const xmas95 = new Date("1995-12-25T23:15:30");
const fullYear = xmas95.getFullYear();

console.log(fullYear); // 1995

“Date.prototype.getFullYear() - JavaScript | MDN” (MDN Web Docs). Retrieved March 20, 2024.

Question 6

Q

Date.prototype.getHours()

Answer

A

The getHours() method of Date instances returns the hours for this date according to local time.

Syntax

getHours()

Parameters
None.

Return value
An integer, between 0 and 23, representing the hours for the given date according to local time. Returns NaN if the date is invalid.

Examples:

const xmas95 = new Date("1995-12-25T23:15:30");
const hours = xmas95.getHours();

console.log(hours); // 23

“Date.prototype.getHours() - JavaScript | MDN” (MDN Web Docs). Retrieved March 21, 2024.

Question 7

Q

Date.prototype.getMilliseconds()

Answer

A

The getMilliseconds() method of Date instances returns the milliseconds for this date according to local time.

Syntax

getMilliseconds()

Parameters
None.

Return value
An integer, between 0 and 999, representing the milliseconds for the given date according to local time. Returns NaN if the date is invalid.

Examples:

const xmas95 = new Date("1995-12-25T23:15:30");
const milliseconds = xmas95.getMilliseconds();

console.log(milliseconds); // 0

“Date.prototype.getMilliseconds() - JavaScript | MDN” (MDN Web Docs). Retrieved March 21, 2024.

Question 8

Q

Date.prototype.getMinutes()

Answer

A

The getMinutes() method of Date instances returns the minutes for this date according to local time.

Syntax

getMinutes()

Parameters
None.

Return value
An integer, between 0 and 59, representing the minutes for the given date according to local time. Returns NaN if the date is invalid.

Examples:

const xmas95 = new Date("1995-12-25T23:15:30");
const minutes = xmas95.getMinutes();

console.log(minutes); // 15

“Date.prototype.getMinutes() - JavaScript | MDN” (MDN Web Docs). Retrieved March 21, 2024.

Question 9

Q

Date.prototype.getMonth()

Answer

A

The getMonth() method of Date instances returns the month for this date according to local time, as a zero-based value (where zero indicates the first month of the year).

The return value of getMonth() is zero-based, which is useful for indexing into arrays of months, for example:

Syntax

getMonth()

Parameters
None.

Return value
An integer, between 0 and 11, representing the month for the given date according to local time: 0 for January, 1 for February, and so on. Returns NaN if the date is invalid.

Examples:

const valentines = new Date("1995-02-14");
const month = valentines.getMonth();
const monthNames = ["January", "February", "March" /* , … */];

console.log(monthNames[month]); // "February"

“Date.prototype.getMonth() - JavaScript | MDN” (MDN Web Docs). Retrieved March 21, 2024.

Question 10

Q

Date.prototype.getSeconds()

Answer

A

The getSeconds() method of Date instances returns the seconds for this date according to local time.

Syntax

getSeconds()

Parameters
None.

Return value
An integer, between 0 and 59, representing the seconds for the given date according to local time. Returns NaN if the date is invalid.

Examples:

const xmas95 = new Date("1995-12-25T23:15:30");
const seconds = xmas95.getSeconds();

console.log(seconds); // 30

“Date.prototype.getSeconds() - JavaScript | MDN” (MDN Web Docs). Retrieved March 21, 2024.

Question 11

Q

Date.prototype.getTime()

Answer

A

The getTime() method of Date instances returns the number of milliseconds for this date since the epoch, which is defined as the midnight at the beginning of January 1, 1970, UTC.

Date objects are fundamentally represented by a timestamp, and this method allows you to retrieve the timestamp. You can use this method to help assign a date and time to another Date object. This method is functionally equivalent to the valueOf() method.

Reduced time precision
To offer protection against timing attacks and fingerprinting, the precision of new Date().getTime() might get rounded depending on browser settings. In Firefox, the privacy.reduceTimerPrecision preference is enabled by default and defaults to 2ms. You can also enable privacy.resistFingerprinting, in which case the precision will be 100ms or the value of privacy.resistFingerprinting, reduceTimerPrecision.microseconds, whichever is larger.

// reduced time precision (2ms) in Firefox 60
new Date().getTime();
// 1519211809934
// 1519211810362
// 1519211811670
// …

// reduced time precision with `privacy.resistFingerprinting` enabled
new Date().getTime();
// 1519129853500
// 1519129858900
// 1519129864400
// …

Syntax

getTime()

Parameters
None.

Return value
A number representing the timestamp, in milliseconds, of this date. Returns NaN if the date is invalid.

Examples:

// Since month is zero based, birthday will be January 10, 1995
const birthday = new Date(1994, 12, 10);
const copy = new Date();
copy.setTime(birthday.getTime());

Note: In browsers that support the Web Performance API’s high-resolution time feature, Performance.now() can provide more reliable and precise measurements of elapsed time than Date.now().

“Date.prototype.getTime() - JavaScript | MDN” (MDN Web Docs). Retrieved March 21, 2024.

Question 12

Q

Date.prototype.getTimezoneOffset()

Answer

A

The getTimezoneOffset() method of Date instances returns the difference, in minutes, between this date as evaluated in the UTC time zone, and the same date as evaluated in the local time zone.

Negative values and positive values

The number of minutes returned by getTimezoneOffset() is positive if the local time zone is behind UTC, and negative if the local time zone is ahead of UTC. For example, for UTC+10, -600 will be returned.

Syntax

getTimezoneOffset()

Parameters
None.

Return value
A number representing the difference, in minutes, between the date as evaluated in the UTC time zone and as evaluated in the local time zone. The actual local time algorithm is implementation-defined, and the return value is allowed to be zero in runtimes without appropriate data. Returns NaN if the date is invalid.

Examples:

// Create a Date instance for the current time
const currentLocalDate = new Date();
// Create a Date instance for 03:24 GMT-0200 on May 1st in 2016
const laborDay2016at0324GMTminus2 = new Date("2016-05-01T03:24:00-02:00");
currentLocalDate.getTimezoneOffset() ===
  laborDay2016at0324GMTminus2.getTimezoneOffset();
// true, always, in any timezone that doesn't annually shift in and out of DST
// false, sometimes, in any timezone that annually shifts in and out of DST

“Date.prototype.getTimezoneOffset() - JavaScript | MDN” (MDN Web Docs). Retrieved March 22, 2024.

Question 13

Q

Date.prototype.getUTCDate()

Answer

A

The getUTCDate() method of Date instances returns the day of the month for this date according to universal time.

Syntax

getUTCDate()

Parameters
None.

Return value
An integer, between 1 and 31, representing day of month for the given date according to universal time. Returns NaN if the date is invalid.

Examples:

const today = new Date();
const dayOfMonth = today.getUTCDate();

“Date.prototype.getUTCDate() - JavaScript | MDN” (MDN Web Docs). Retrieved March 22, 2024.

Question 14

Q

Date.prototype.getUTCDay()

Answer

A

The getUTCDay() method of Date instances returns the day of the week for this date according to universal time, where 0 represents Sunday.

Syntax

getUTCDay()

Parameters
None.

Return value
An integer corresponding to the day of the week for the given date according to universal time: 0 for Sunday, 1 for Monday, 2 for Tuesday, and so on. Returns NaN if the date is invalid.

Examples:

const today = new Date();
const weekday = today.getUTCDay();

“Date.prototype.getUTCDay() - JavaScript | MDN” (MDN Web Docs). Retrieved March 22, 2024.

Question 15

Q

Date.prototype.getUTCFullYear()

Answer

A

The getUTCFullYear() method of Date instances returns the year for this date according to universal time.

Unlike getYear(), the value returned by getUTCFullYear() is an absolute number. For dates between the years 1000 and 9999, getUTCFullYear() returns a four-digit number, for example, 1995. Use this function to make sure a year is compliant with years after 2000.

Syntax

getUTCFullYear()

Parameters
None.

Return value
An integer representing the year for the given date according to universal time. Returns NaN if the date is invalid.

Examples:

const today = new Date();
const year = today.getUTCFullYear();

“Date.prototype.getUTCFullYear() - JavaScript | MDN” (MDN Web Docs). Retrieved March 22, 2024.

Question 16

Q

Date.prototype.getUTCHours()

Answer

A

The getUTCHours() method of Date instances returns the hours for this date according to universal time.

Syntax

getUTCHours()

Parameters
None.

Return value
An integer, between 0 and 23, representing the hours for the given date according to universal time. Returns NaN if the date is invalid.

Examples:

const today = new Date();
const hours = today.getUTCHours();

“Date.prototype.getUTCHours() - JavaScript | MDN” (MDN Web Docs). Retrieved March 25, 2024.

Question 17

Q

Date.prototype.getUTCMilliseconds()

Answer

A

The getUTCMilliseconds() method of Date instances returns the milliseconds for this date according to universal time.

Syntax

getUTCMilliseconds()

Parameters

None.

Return value
An integer, between 0 and 999, representing the milliseconds for the given date according to universal time. Returns NaN if the date is invalid.

Not to be confused with the timestamp. To get the total milliseconds since the epoch, use the getTime() method.

Examples:

const today = new Date();
const milliseconds = today.getUTCMilliseconds();

“Date.prototype.getUTCMilliseconds() - JavaScript | MDN” (MDN Web Docs). Retrieved March 25, 2024.

Question 18

Q

Date.prototype.getUTCMinutes()

Answer

A

The getUTCMinutes() method of Date instances returns the minutes for this date according to universal time.

Syntax

getUTCMinutes()

Parameters
None.

Return value
An integer, between 0 and 59, representing the minutes for the given date according to universal time. Returns NaN if the date is invalid.

Examples

const today = new Date();
const minutes = today.getUTCMinutes();

“Date.prototype.getUTCMinutes() - JavaScript | MDN” (MDN Web Docs). Retrieved March 25, 2024.

Question 19

Q

Date.prototype.getUTCMonth()

Answer

A

The getUTCMonth() method of Date instances returns the month for this date according to universal time, as a zero-based value (where zero indicates the first month of the year).

Syntax

getUTCMonth()

Parameters
None.

Return value
An integer, between 0 and 11, representing the month for the given date according to universal time: 0 for January, 1 for February, and so on. Returns NaN if the date is invalid.

Examples:

const today = new Date();
const month = today.getUTCMonth();

“Date.prototype.getUTCMonth() - JavaScript | MDN” (MDN Web Docs). Retrieved March 25, 2024.

Question 20

Q

Date.prototype.getUTCSeconds()

Answer

A

The getUTCSeconds() method of Date instances returns the seconds in the specified date according to universal time.

Syntax

getUTCSeconds()

Parameters
None.

Return value
An integer, between 0 and 59, representing the seconds for the given date according to universal time. Returns NaN if the date is invalid.

Examples:

const today = new Date();
const seconds = today.getUTCSeconds();

“Date.prototype.getUTCSeconds() - JavaScript | MDN” (MDN Web Docs). Retrieved March 25, 2024.

Question 21

Q

Date.prototype.getYear()

Answer

A

Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards.

The getYear() method of Date instances returns the year for this date according to local time. Because getYear() does not return full years (“year 2000 problem”), it is deprecated and has been replaced by the getFullYear() method.

Syntax

getYear()

Parameters
None.

Return value
An integer representing the year for the given date according to local time, minus 1900. Returns NaN if the date is invalid.

For years greater than or equal to 2000, the value is 100 or greater. For example, if the year is 2026, getYear() returns 126.
For years between and including 1900 and 1999, the value returned by getYear() is between 0 and 99. For example, if the year is 1976, getYear() returns 76.
For years less than 1900, the value returned by getYear() is less than ç. For example, if the year is 1800, getYear() returns -100.
This method essentially returns the value of getFullYear() minus 1900. You should use getFullYear() instead, so that the year is specified in full.

Examples:

// Years between 1900 and 1999
let xmas = new Date("1995-12-25");
let year = xmas.getYear(); // returns 95

// Years above 1999
xmas = new Date("2000-12-25");
year = xmas.getYear(); // returns 100

// Years below 1900
xmas = new Date("1800-12-25");
year = xmas.getYear(); // returns -100

“Date.prototype.getYear() - JavaScript | MDN” (MDN Web Docs). Retrieved March 25, 2024.

Question 22

Q

Date.now()

Answer

A

The Date.now() static method returns the number of milliseconds elapsed since the epoch, which is defined as the midnight at the beginning of January 1, 1970, UTC.

Reduced time precision
To offer protection against timing attacks and fingerprinting, the precision of Date.now() might get rounded depending on browser settings.

Syntax

Date.now()

Parameters
None.

Return value
A number representing the timestamp, in milliseconds, of the current time.

“Date.now() - JavaScript | MDN” (MDN Web Docs). Retrieved March 26, 2024.

Question 23

Q

Date.parse()

Answer

A

The Date.parse() static method parses a string representation of a date, and returns the date’s timestamp.

Syntax

Date.parse(dateString)

Parameters

dateString - A string in the date time string format.

Return value
A number representing the timestamp of the given date. If dateString fails to be parsed as a valid date, NaN is returned.

Examples:

The following calls all return 1546300800000. The first will imply UTC time because it’s date-only, and the others explicitly specify the UTC timezone.

Date.parse("2019-01-01");
Date.parse("2019-01-01T00:00:00.000Z");
Date.parse("2019-01-01T00:00:00.000+00:00");

“Date.parse() - JavaScript | MDN” (MDN Web Docs). Retrieved March 26, 2024.

Question 24

Q

Date.prototype.setDate()

Answer

A

The setDate() method of Date instances changes the day of the month for this date according to local time.

Syntax

setDate(dateValue)

Parameters

dateValue - An integer representing the day of the month.

Return value

Changes the Date object in place, and returns its new timestamp. If dateValue is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Examples:

const theBigDay = new Date(1962, 6, 7, 12); // noon of 1962-07-07 (7th of July 1962, month is 0-indexed)
const theBigDay2 = new Date(theBigDay).setDate(24); // 1962-07-24 (24th of July 1962)
const theBigDay3 = new Date(theBigDay).setDate(32); // 1962-08-01 (1st of August 1962)
const theBigDay4 = new Date(theBigDay).setDate(22); // 1962-07-22 (22nd of July 1962)
const theBigDay5 = new Date(theBigDay).setDate(0); // 1962-06-30 (30th of June 1962)
const theBigDay6 = new Date(theBigDay).setDate(98); // 1962-10-06 (6th of October 1962)
const theBigDay7 = new Date(theBigDay).setDate(-50); // 1962-05-11 (11th of May 1962)

“Date.prototype.setDate() - JavaScript | MDN” (MDN Web Docs). Retrieved March 26, 2024.

Question 25

Q

Date.prototype.setFullYear()

Answer

A

The setFullYear() method of Date instances changes the year, month, and/or day of month for this date according to local time.

Syntax

setFullYear(yearValue)
setFullYear(yearValue, monthValue)
setFullYear(yearValue, monthValue, dateValue)

Parameters

yearValue - An integer representing the year. For example, 1995.
monthValue Optional - An integer representing the month: 0 for January, 1 for February, and so on.
dateValue Optional - An integer between 1 and 31 representing the day of the month. If you specify dateValue, you must also specify monthValue.

Return value
Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

“Date.prototype.setFullYear() - JavaScript | MDN” (MDN Web Docs). Retrieved March 26, 2024.

Question 26

Q

Date.prototype.setHours()

Answer

A

The setHours() method of Date instances changes the hours, minutes, seconds, and/or milliseconds for this date according to local time.

Syntax

setHours(hoursValue)
setHours(hoursValue, minutesValue)
setHours(hoursValue, minutesValue, secondsValue)
setHours(hoursValue, minutesValue, secondsValue, msValue)

Parameters

hoursValue - An integer between 0 and 23 representing the hours.
minutesValue Optional - An integer between 0 and 59 representing the minutes.
secondsValue Optional - An integer between 0 and 59 representing the seconds. If you specify secondsValue, you must also specify minutesValue.
msValue Optional - An integer between 0 and 999 representing the milliseconds. If you specify msValue, you must also specify minutesValue and secondsValue.

Description

If you do not specify the minutesValue, secondsValue, and msValue parameters, the same values as what are returned by getMinutes(), getSeconds(), and getMilliseconds() are used.

If a parameter you specify is outside of the expected range, other parameters and the date information in the Date object are updated accordingly. For example, if you specify 100 for secondsValue, the minutes are incremented by 1 (minutesValue + 1), and 40 is used for seconds.

Return value
Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Examples:

const theBigDay = new Date();
theBigDay.setHours(7);

“Date.prototype.setHours() - JavaScript | MDN” (MDN Web Docs). Retrieved March 27, 2024.

Question 27

Q

Date.prototype.setMilliseconds()

Answer

A

The setMilliseconds() method of Date instances changes the milliseconds for this date according to local time.

Syntax

setMilliseconds(millisecondsValue)

Parameters

millisecondsValue - An integer between 0 and 999 representing the milliseconds.

Return value
Changes the Date object in place, and returns its new timestamp. If millisecondsValue is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If you specify a number outside the expected range, the date information in the Date object is updated accordingly. For example, if you specify 1005, the number of seconds is incremented by 1, and 5 is used for the milliseconds.

Examples:

const theBigDay = new Date();
theBigDay.setMilliseconds(100);

“Date.prototype.setMilliseconds() - JavaScript | MDN” (MDN Web Docs). Retrieved March 27, 2024.

Question 28

Q

Date.prototype.setMinutes()

Answer

A

The setMinutes() method of Date instances changes the minutes for this date according to local time.

Syntax

setMinutes(minutesValue)
setMinutes(minutesValue, secondsValue)
setMinutes(minutesValue, secondsValue, msValue)

Parameters

minutesValue - An integer between 0 and 59 representing the minutes.
secondsValue Optional - An integer between 0 and 59 representing the seconds. If you specify secondsValue, you must also specify minutesValue.
msValue Optional - An integer between 0 and 999 representing the milliseconds. If you specify msValue, you must also specify minutesValue and secondsValue.

Return value
Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If you do not specify the secondsValue and msValue parameters, the same values as what are returned by getSeconds() and getMilliseconds() are used.

If a parameter you specify is outside of the expected range, other parameters and the date information in the Date object are updated accordingly. For example, if you specify 100 for secondsValue, the minutes is incremented by 1 (minutesValue + 1), and 40 is used for seconds.

Examples:

const theBigDay = new Date();
theBigDay.setMinutes(45);

“Date.prototype.setMinutes() - JavaScript | MDN” (MDN Web Docs). Retrieved March 27, 2024.

Question 29

Q

Date.prototype.setMonth()

Answer

A

The setMonth() method of Date instances changes the month and/or day of the month for this date according to local time.

Syntax

setMonth(monthValue)
setMonth(monthValue, dateValue)

Parameters

monthValue - An integer representing the month: 0 for January, 1 for February, and so on.
dateValue Optional - An integer from 1 to 31 representing the day of the month.

Return value
Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If you do not specify the dateValue parameter, the same value as what is returned by getDate() is used.

If a parameter you specify is outside of the expected range, other parameters and the date information in the Date object are updated accordingly. For example, if you specify 15 for monthValue, the year is incremented by 1, and 3 is used for month.

The current day of month will have an impact on the behavior of this method. Conceptually it will add the number of days given by the current day of the month to the 1st day of the new month specified as the parameter, to return the new date. For example, if the current value is 31st January 2016, calling setMonth with a value of 1 will return 2nd March 2016. This is because in 2016 February had 29 days.

Examples:

theBigDay.setMonth(6);

//Watch out for end of month transitions
const endOfMonth = new Date(2016, 7, 31);
endOfMonth.setMonth(1);
console.log(endOfMonth); //Wed Mar 02 2016 00:00:00

“Date.prototype.setMonth() - JavaScript | MDN” (MDN Web Docs). Retrieved March 27, 2024.

Question 30

Q

Date.prototype.setSeconds()

Answer

A

The setSeconds() method of Date instances changes the seconds and/or milliseconds for this date according to local time.

Syntax

setSeconds(secondsValue)
setSeconds(secondsValue, msValue)

Parameters

secondsValue - An integer between 0 and 59 representing the seconds.
msValue Optional - An integer between 0 and 999 representing the milliseconds.

Return value
Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If you do not specify the msValue parameter, the value returned from the getMilliseconds() method is used.

If a parameter you specify is outside of the expected range, setSeconds() attempts to update the date information in the Date object accordingly. For example, if you use 100 for secondsValue, the minutes stored in the Date object will be incremented by 1, and 40 will be used for seconds.

Examples:

const theBigDay = new Date();
theBigDay.setSeconds(30);

“Date.prototype.setSeconds() - JavaScript | MDN” (MDN Web Docs). Retrieved March 28, 2024.

Question 31

Q

Date.prototype.setTime()

Answer

A

The setTime() method of Date instances changes the timestamp for this date, which is the number of milliseconds since the epoch, defined as the midnight at the beginning of January 1, 1970, UTC.

Syntax

setTime(timeValue)

Parameters

timeValue - An integer representing the new timestamp — the number of milliseconds since the midnight at the beginning of January 1, 1970, UTC.

Return value
Changes the Date object in place, and returns its new timestamp. If timeValue is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Examples:

const theBigDay = new Date("1999-07-01");
const sameAsBigDay = new Date();
sameAsBigDay.setTime(theBigDay.getTime());

“Date.prototype.setTime() - JavaScript | MDN” (MDN Web Docs). Retrieved March 28, 2024.

Question 32

Q

Date.prototype.setUTCDate()

Answer

A

The setUTCDate() method of Date instances changes the day of the month for this date according to universal time.

Syntax

setUTCDate(dateValue)

Parameters

dateValue - An integer from 1 to 31 representing the day of the month.

Return value
Changes the Date object in place, and returns its new timestamp. If dateValue is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If the dateValue is outside of the range of date values for the month, setDate() will update the Date object accordingly.

For example, if 0 is provided for dateValue, the date will be set to the last day of the previous month. If you use 40 for dateValue, and the month stored in the Date object is June, the day will be changed to 10 and the month will be incremented to July.

If a negative number is provided for dateValue, the date will be set counting backwards from the last day of the previous month. -1 would result in the date being set to 1 day before the last day of the previous month.

Examples:

const theBigDay = new Date();
theBigDay.setUTCDate(20);

“Date.prototype.setUTCDate() - JavaScript | MDN” (MDN Web Docs). Retrieved March 28, 2024.

Question 33

Q

Date.prototype.setUTCFullYear()

Answer

A

The setUTCFullYear() method of Date instances changes the year for this date according to universal time.

Syntax

setUTCFullYear(yearValue)
setUTCFullYear(yearValue, monthValue)
setUTCFullYear(yearValue, monthValue, dateValue)

Parameters

yearValue - An integer representing the year. For example, 1995.
monthValue Optional - An integer representing the month: 0 for January, 1 for February, and so on.
dateValue Optional - An integer between 1 and 31 representing the day of the month. If you specify dateValue, you must also specify monthValue.

Return value
Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If you do not specify the monthValue and dateValue parameters, the values returned from the getUTCMonth() and getUTCDate() methods are used.

If a parameter you specify is outside of the expected range, setUTCFullYear() attempts to update the other parameters and the date information in the Date object accordingly. For example, if you specify 15 for monthValue, the year is incremented by 1 (yearValue + 1), and 3 is used for the month.

Examples

const theBigDay = new Date();
theBigDay.setUTCFullYear(1997);

“Date.prototype.setUTCFullYear() - JavaScript | MDN” (MDN Web Docs). Retrieved March 28, 2024.

Question 34

Q

Date.prototype.setUTCHours()

Answer

A

The setUTCHours() method of Date instances changes the hours, minutes, seconds, and/or milliseconds for this date according to universal time.

Syntax

setUTCHours(hoursValue)
setUTCHours(hoursValue, minutesValue)
setUTCHours(hoursValue, minutesValue, secondsValue)
setUTCHours(hoursValue, minutesValue, secondsValue, msValue)

Parameters

hoursValue - An integer between 0 and 23 representing the hours.
minutesValue Optional - An integer between 0 and 59 representing the minutes.
secondsValue Optional - An integer between 0 and 59 representing the seconds. If you specify secondsValue, you must also specify minutesValue.
msValue Optional - An integer between 0 and 999 representing the milliseconds. If you specify msValue, you must also specify minutesValue and secondsValue.

Return value

Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If you do not specify the minutesValue, secondsValue, and msValue parameters, the values returned from the getUTCMinutes(), getUTCSeconds(), and getUTCMilliseconds() methods are used.

If a parameter you specify is outside of the expected range, setUTCHours() attempts to update the date information in the Date object accordingly. For example, if you use 100 for secondsValue, the minutes will be incremented by 1 (minutesValue + 1), and 40 will be used for seconds.

Examples:

const theBigDay = new Date();
theBigDay.setUTCHours(8);

“Date.prototype.setUTCHours() - JavaScript | MDN” (MDN Web Docs). Retrieved March 28, 2024.

Question 35

Q

Date.prototype.setUTCMilliseconds()

Answer

A

The setUTCMilliseconds() method of Date instances changes the milliseconds for this date according to universal time.

Syntax

setUTCMilliseconds(millisecondsValue)

Parameters

millisecondsValue - An integer between 0 and 999 representing the milliseconds.

Return value

Changes the Date object in place, and returns its new timestamp. If millisecondsValue is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description

If a parameter you specify is outside of the expected range, setUTCMilliseconds() attempts to update the date information in the Date object accordingly. For example, if you use 1100 for millisecondsValue, the seconds stored in the Date object will be incremented by 1, and 100 will be used for milliseconds.

Examples:

const theBigDay = new Date();
theBigDay.setUTCMilliseconds(500);

“Date.prototype.setUTCMilliseconds() - JavaScript | MDN” (MDN Web Docs). Retrieved March 29, 2024.

Question 36

Q

Date.prototype.setUTCMinutes()

Answer

A

The setUTCMinutes() method of Date instances changes the minutes for this date according to universal time.

Syntax

setUTCMinutes(minutesValue)
setUTCMinutes(minutesValue, secondsValue)
setUTCMinutes(minutesValue, secondsValue, msValue)

Parameters

minutesValue - An integer between 0 and 59 representing the minutes.
secondsValue Optional - An integer between 0 and 59 representing the seconds. If you specify secondsValue, you must also specify minutesValue.
msValue Optional - An integer between 0 and 999 representing the milliseconds. If you specify msValue, you must also specify minutesValue and secondsValue.

Return value
Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If you do not specify the secondsValue and msValue parameters, the values returned from getUTCSeconds(), and getUTCMilliseconds() methods are used.

If a parameter you specify is outside of the expected range, setUTCMinutes() attempts to update the date information in the Date object accordingly. For example, if you use 100 for secondsValue, the minutes will be incremented by 1 (minutesValue + 1), and 40 will be used for seconds.

Examples:

const theBigDay = new Date();
theBigDay.setUTCMinutes(43);

“Date.prototype.setUTCMinutes() - JavaScript | MDN” (MDN Web Docs). Retrieved March 29, 2024.

Question 37

Q

Date.prototype.setUTCMonth()

Answer

A

The setUTCMonth() method of Date instances changes the month and/or day of the month for this date according to universal time.

Syntax

setUTCMonth(monthValue)
setUTCMonth(monthValue, dateValue)

Parameters

monthValue - An integer representing the month: 0 for January, 1 for February, and so on.
dateValue Optional - An integer from 1 to 31 representing the day of the month.

Return value
Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If you do not specify the dateValue parameter, the value returned from the getUTCDate() method is used.

If a parameter you specify is outside of the expected range, setUTCMonth() attempts to update the date information in the Date object accordingly. For example, if you use 15 for monthValue, the year will be incremented by 1, and 3 will be used for month.

Examples:

const theBigDay = new Date();
theBigDay.setUTCMonth(11);

“Date.prototype.setUTCMonth() - JavaScript | MDN” (MDN Web Docs). Retrieved March 29, 2024.

Question 38

Q

Date.prototype.setUTCSeconds()

Answer

A

The setUTCSeconds() method of Date instances changes the seconds and/or milliseconds for this date according to universal time.

Syntax

setUTCSeconds(secondsValue)
setUTCSeconds(secondsValue, msValue)

Parameters

secondsValue - An integer between 0 and 59 representing the seconds.
msValue Optional - An integer between 0 and 999 representing the milliseconds.

Return value

Changes the Date object in place, and returns its new timestamp. If a parameter is NaN (or other values that get coerced to NaN, such as undefined), the date is set to Invalid Date and NaN is returned.

Description
If you do not specify the msValue parameter, the value returned from the getUTCMilliseconds() method is used.

If a parameter you specify is outside of the expected range, setUTCSeconds() attempts to update the date information in the Date object accordingly. For example, if you use 100 for secondsValue, the minutes stored in the Date object will be incremented by 1, and 40 will be used for seconds.

Examples:

const theBigDay = new Date();
theBigDay.setUTCSeconds(20);

“Date.prototype.setUTCSeconds() - JavaScript | MDN” (MDN Web Docs). Retrieved April 2, 2024.

Question 39

Q

Date.prototype.toDateString()

Answer

A

The toDateString() method of Date instances returns a string representing the date portion of this date interpreted in the local timezone.

Syntax

toDateString()

Parameters
None.

Return value
A string representing the date portion of the given date. Returns "Invalid Date" if the date is invalid.

Description

Date instances refer to a specific point in time. toDateString() interprets the date in the local timezone and formats the date part in English. It always uses the following format, separated by spaces:

First three letters of the week day name
First three letters of the month name
Two-digit day of the month, padded on the left a zero if necessary
Four-digit year (at least), padded on the left with zeros if necessary.

May have a negative sign
For example: "Thu Jan 01 1970".

If you only want to get the time part, use toTimeString().
If you want to get both the date and time, use toString().
If you want to make the date interpreted as UTC instead of local timezone, use toUTCString().
If you want to format the date in a more user-friendly format (e.g. localization), use toLocaleDateString().

Examples:

const d = new Date(0);

console.log(d.toString()); // "Thu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)"
console.log(d.toDateString()); // "Thu Jan 01 1970"

“Date.prototype.toDateString() - JavaScript | MDN” (MDN Web Docs). Retrieved April 2, 2024.

Question 40

Q

Date.prototype.toISOString()

Answer

A

The toISOString() method of Date instances returns a string representing this date in the date time string format, a simplified format based on ISO 8601, which is always 24 or 27 characters long (YYYY-MM-DDTHH:mm:ss.sssZ or ±YYYYYY-MM-DDTHH:mm:ss.sssZ, respectively). The timezone is always UTC, as denoted by the suffix Z.

Syntax

toISOString()

Parameters

None.

Return value

A string representing the given date in the date time string format according to universal time. It’s the same format as the one required to be recognized by Date.parse().

Exceptions

RangeError - Thrown if the date is invalid or if it corresponds to a year that cannot be represented in the date string format.

Examples

const d = new Date(0);

console.log(d.toISOString()); // "1970-01-01T00:00:00.000Z"

“Date.prototype.toISOString() - JavaScript | MDN” (MDN Web Docs). Retrieved April 2, 2024.

Question 41

Q

Date.prototype.toJSON()

Answer

A

The toJSON() method of Date instances returns a string representing this date in the same ISO format as toISOString().

Syntax

toJSON()

Parameters
None.

Return value
A string representing the given date in the date time string format according to universal time, or null when the date is invalid. For valid dates, the return value is the same as that of toISOString().

Examples:

const jsonDate = new Date(0).toJSON(); // '1970-01-01T00:00:00.000Z'
const backToDate = new Date(jsonDate);

console.log(jsonDate); // 1970-01-01T00:00:00.000Z

“Date.prototype.toJSON() - JavaScript | MDN” (MDN Web Docs). Retrieved April 2, 2024.

Question 42

Q

Date.prototype.toLocaleDateString()

Answer

A

The toLocaleDateString() method of Date instances returns a string with a language-sensitive representation of the date portion of this date in the local timezone. In implementations with Intl.DateTimeFormat API support, this method simply calls Intl.DateTimeFormat.

Syntax

toLocaleDateString()
toLocaleDateString(locales)
toLocaleDateString(locales, options)

Parameters
The locales and options parameters customize the behavior of the function and let applications specify the language whose formatting conventions should be used.

locales Optional - A string with a BCP 47 language tag, or an array of such strings. Corresponds to the locales parameter of the Intl.DateTimeFormat() constructor.
options Optional - An object adjusting the output format. Corresponds to the options parameter of the Intl.DateTimeFormat() constructor. The timeStyle option must be undefined, or a TypeError would be thrown. If weekday, year, month, and day are all undefined, then year, month, and day will be set to "numeric".

See the Intl.DateTimeFormat() constructor for details on these parameters and how to use them.

Return value

A string representing the date portion of the given date according to language-specific conventions.

Note: Most of the time, the formatting returned by toLocaleDateString() is consistent. However, the output may vary with time, language, and implementation — output variations are by design and allowed by the specification. You should not compare the results of toLocaleDateString() to static values.

Examples:

const date = new Date(Date.UTC(2012, 11, 20, 3, 0, 0));

// formats below assume the local time zone of the locale;
// America/Los_Angeles for the US

// US English uses month-day-year order
console.log(date.toLocaleDateString("en-US"));
// "12/20/2012"

// British English uses day-month-year order
console.log(date.toLocaleDateString("en-GB"));
// "20/12/2012"

// Korean uses year-month-day order
console.log(date.toLocaleDateString("ko-KR"));
// "2012. 12. 20."

// Event for Persian, It's hard to manually convert date to Solar Hijri
console.log(date.toLocaleDateString("fa-IR"));
// "۱۳۹۱/۹/۳۰"

// Arabic in most Arabic speaking countries uses real Arabic digits
console.log(date.toLocaleDateString("ar-EG"));
// "٢٠‏/١٢‏/٢٠١٢"

// for Japanese, applications may want to use the Japanese calendar,
// where 2012 was the year 24 of the Heisei era
console.log(date.toLocaleDateString("ja-JP-u-ca-japanese"));
// "24/12/20"

// when requesting a language that may not be supported, such as
// Balinese, include a fallback language, in this case Indonesian
console.log(date.toLocaleDateString(["ban", "id"]));
// "20/12/2012"

“Date.prototype.toLocaleDateString() - JavaScript | MDN” (MDN Web Docs). Retrieved April 3, 2024.j

Question 43

Q

Date.prototype.toLocaleString()

Answer

A

The toLocaleString() method of Date instances returns a string with a language-sensitive representation of this date in the local timezone.

Syntax

toLocaleString()
toLocaleString(locales)
toLocaleString(locales, options)

Parameters

The locales and options parameters customize the behavior of the function and let applications specify the language whose formatting conventions should be used.

locales Optional - A string with a BCP 47 language tag, or an array of such strings. Corresponds to the locales parameter of the Intl.DateTimeFormat() constructor.
options Optional - An object adjusting the output format. Corresponds to the options parameter of the Intl.DateTimeFormat() constructor. If weekday, year, month, day, dayPeriod, hour, minute, second, and fractionalSecondDigits are all undefined, then year, month, day, hour, minute, second will be set to "numeric".

See the Intl.DateTimeFormat() constructor for details on these parameters and how to use them.

Return value
A string representing the given date according to language-specific conventions.

In implementations with Intl.DateTimeFormat, this is equivalent to new Intl.DateTimeFormat(locales, options).format(date).

Note: Most of the time, the formatting returned by toLocaleString() is consistent. However, the output may vary with time, language, and implementation — output variations are by design and allowed by the specification. You should not compare the results of toLocaleString() to static values.

Examples:

const date = new Date(Date.UTC(2012, 11, 20, 3, 0, 0));

// Formats below assume the local time zone of the locale;
// America/Los_Angeles for the US

// US English uses month-day-year order and 12-hour time with AM/PM
console.log(date.toLocaleString("en-US"));
// "12/19/2012, 7:00:00 PM"

// British English uses day-month-year order and 24-hour time without AM/PM
console.log(date.toLocaleString("en-GB"));
// "20/12/2012 03:00:00"

// Korean uses year-month-day order and 12-hour time with AM/PM
console.log(date.toLocaleString("ko-KR"));
// "2012. 12. 20. 오후 12:00:00"

// Arabic in most Arabic-speaking countries uses Eastern Arabic numerals
console.log(date.toLocaleString("ar-EG"));
// "٢٠‏/١٢‏/٢٠١٢ ٥:٠٠:٠٠ ص"

// For Japanese, applications may want to use the Japanese calendar,
// where 2012 was the year 24 of the Heisei era
console.log(date.toLocaleString("ja-JP-u-ca-japanese"));
// "24/12/20 12:00:00"

// When requesting a language that may not be supported, such as
// Balinese, include a fallback language (in this case, Indonesian)
console.log(date.toLocaleString(["ban", "id"]));
// "20/12/2012 11.00.00"

“Date.prototype.toLocaleString() - JavaScript | MDN” (MDN Web Docs). Retrieved April 3, 2024.

Question 44

Q

Date.prototype.toLocaleTimeString()

Answer

A

The toLocaleTimeString() method of Date instances returns a string with a language-sensitive representation of the time portion of this date in the local timezone. In implementations with Intl.DateTimeFormat API support, this method simply calls Intl.DateTimeFormat.

Syntax

toLocaleTimeString()
toLocaleTimeString(locales)
toLocaleTimeString(locales, options)

Parameters

The locales and options parameters customize the behavior of the function and let applications specify the language whose formatting conventions should be used.

locales Optional - A string with a BCP 47 language tag, or an array of such strings. Corresponds to the locales parameter of the Intl.DateTimeFormat() constructor.
options Optional - An object adjusting the output format. Corresponds to the options parameter of the Intl.DateTimeFormat() constructor. If dayPeriod, hour, minute, second, and fractionalSecondDigits are all undefined, then hour, minute, second will be set to "numeric".

See the Intl.DateTimeFormat() constructor for details on these parameters and how to use them.

Return value
A string representing the time portion of the given date according to language-specific conventions.

Note: Most of the time, the formatting returned by toLocaleTimeString() is consistent. However, the output may vary with time, language, and implementation — output variations are by design and allowed by the specification. You should not compare the results of toLocaleTimeString() to static values.

Examples:

const date = new Date(Date.UTC(2012, 11, 12, 3, 0, 0));

// toLocaleTimeString() without arguments depends on the implementation,
// the default locale, and the default time zone
console.log(date.toLocaleTimeString());
// "7:00:00 PM" if run in en-US locale with time zone America/Los_Angeles

“Date.prototype.toLocaleTimeString() - JavaScript | MDN” (MDN Web Docs). Retrieved April 4, 2024.

Question 45

Q

Date.prototype.toString()

Answer

A

Date.prototype.toString() returns a string representation of the Date as interpreted in the local timezone, containing both the date and the time — it joins the string representation specified in toDateString() and toTimeString() together, adding a space in between. For example: "Thu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)".

Syntax

toString()

Parameters
None.

Return value
A string representing the given date. Returns "Invalid Date" if the date is invalid.

Description
The Date object overrides the toString() method of Object.

Examples:

const d = new Date(0);
console.log(d.toString()); // "Thu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)"

“Date.prototype.toString() - JavaScript | MDN” (MDN Web Docs). Retrieved April 4, 2024.

Question 46

Q

Date.prototype.toTimeString()

Answer

A

The toTimeString() method of Date instances returns a string representing the time portion of this date interpreted in the local timezone.

Date instances refer to a specific point in time. toTimeString() interprets the date in the local timezone and formats the time part in English. It always uses the format of hh:mm:ss GMT±xxxx (TZ), where:

hh - Hour, as two digits with leading zero if required
mm - Minute, as two digits with leading zero if required
ss - Seconds, as two digits with leading zero if required
±xxxx - The local timezone’s offset — two digits for hours and two digits for minutes (e.g. -0500, +0800)
TZ - The timezone’s name (e.g. PDT, PST)

For example: "04:42:04 GMT+0000 (Coordinated Universal Time)".

Syntax

toTimeString()

Parameters
None.

Return value
A string representing the time portion of the given date (see description for the format). Returns "Invalid Date" if the date is invalid.

Examples:

const d = new Date(0);

console.log(d.toString()); // "Thu Jan 01 1970 00:00:00 GMT+0000 (Coordinated Universal Time)"
console.log(d.toTimeString()); // "00:00:00 GMT+0000 (Coordinated Universal Time)"

“Date.prototype.toTimeString() - JavaScript | MDN” (MDN Web Docs). Retrieved April 5, 2024.

Question 47

Q

Date.prototype.toUTCString()

Answer

A

The toUTCString() method of Date instances returns a string representing this date in the RFC 7231 format, with negative years allowed. The timezone is always UTC. toGMTString() is an alias of this method.

The value returned by toUTCString() is a string in the form Www, dd Mmm yyyy hh:mm:ss GMT, where:

Www - Day of week, as three letters (e.g. Sun, Mon)
dd - Day of month, as two digits with leading zero if required
Mmm - Month, as three letters (e.g. Jan, Feb)
yyyy - Year, as four or more digits with leading zeroes if required
hh - Hour, as two digits with leading zero if required
mm - Minute, as two digits with leading zero if required
ss - Seconds, as two digits with leading zero if required

Syntax

toUTCString()

Parameters
None.

Return value
A string representing the given date using the UTC time zone (see description for the format). Returns "Invalid Date" if the date is invalid.

Examples:

const d = new Date(0);
console.log(d.toUTCString()); // 'Thu, 01 Jan 1970 00:00:00 GMT'

“Date.prototype.toUTCString() - JavaScript | MDN” (MDN Web Docs). Retrieved April 5, 2024.

Question 48

Q

Date.UTC()

Answer

A

The Date.UTC() static method accepts parameters representing the date and time components similar to the Date constructor, but treats them as UTC. It returns the number of milliseconds since January 1, 1970, 00:00:00 UTC.

If a parameter is outside of the expected range, the UTC() method updates the other parameters to accommodate the value. For example, if 15 is used for monthIndex, the year will be incremented by 1 (year + 1) and 3 will be used for the month.

The UTC() method differs from the Date() constructor in three ways:

Date.UTC() uses universal time instead of the local time.
Date.UTC() returns a time value as a number instead of creating a Date object.
When passed a single number, Date.UTC() interprets it as a year instead of a timestamp.

Syntax

Date.UTC(year)
Date.UTC(year, monthIndex)
Date.UTC(year, monthIndex, day)
Date.UTC(year, monthIndex, day, hour)
Date.UTC(year, monthIndex, day, hour, minute)
Date.UTC(year, monthIndex, day, hour, minute, second)
Date.UTC(year, monthIndex, day, hour, minute, second, millisecond)

Parameters

year - Integer value representing the year. Values from 0 to 99 map to the years 1900 to 1999. All other values are the actual year.
monthIndex Optional - Integer value representing the month, beginning with 0 for January to 11 for December. Defaults to 0.
day Optional - Integer value representing the day of the month. Defaults to 1.
hours Optional - Integer value between 0 and 23 representing the hour of the day. Defaults to 0.
minutes Optional - Integer value representing the minute segment of a time. Defaults to 0.
seconds Optional - Integer value representing the second segment of a time. Defaults to 0.
milliseconds Optional - Integer value representing the millisecond segment of a time. Defaults to 0.

Return value
A number representing the timestamp of the given date. Returns NaN if the date is invalid.

Examples:

const utcDate = new Date(Date.UTC(2018, 11, 1, 0, 0, 0));
Date.UTC(2017); // 1483228800000

“Date.UTC() - JavaScript | MDN” (MDN Web Docs). Retrieved April 5, 2024.

Question 49

Q

Date.prototype.valueOf()

Answer

A

The valueOf() method of Date instances returns the number of milliseconds for this date since the epoch, which is defined as the midnight at the beginning of January 1, 1970, UTC.

Syntax

valueOf()

Parameters
None.

Return value
A number representing the timestamp, in milliseconds, of this date. Returns NaN if the date is invalid.

Examples:

const d = new Date(0); // 1970-01-01T00:00:00.000Z
console.log(d.valueOf()); // 0

“Date.prototype.valueOf() - JavaScript | MDN” (MDN Web Docs). Retrieved April 5, 2024.