Part 6- A Smarter Way to Learn JavaScript

Question 1

Code for converting a string that’s a number to its equivalent number

Answer 1

Number(variableName);

(the name of the variable is at the end)

Note: works for integer strings and floating-point number strings

Question 2

Code for converting a number to a string?

Answer 2

variableName.toString();

(the name of the variable is at the beginning)

Question 3

Limit the decimal places on a number?

Answer 3

varName.toFixed(# of digits);

HOWEVER this also converts it to a string

Question 4

What is the code to get a new date object and assign it to the variable “now”?

Answer 4

var now = new Date();

*notice that “Date” is capitalized

Question 5

In a Date object, what number is assigned to Sunday?

Answer 5

0

Question 6

In a Date object, what number is assigned to Saturday?

Answer 6

6

Question 7

In a Date object, what number is assigned to Thursday?

Answer 7

4

Question 8

How would I extract the day of the week from a Date object called “party”?

Answer 8

party.getDay();

Question 9

What’s the difference between these?
getDate();
getDay();

Answer 9

Date is day of the month
It’s indexed with 1

Day is the day of the week
It’s indexed with 0

Question 10

What does getTime() return from a Date object??

Answer 10

The milliseconds since midnight, January 1, 1970

Question 11

What does getMonth() return from a Date object??

Answer 11

A number. 0 for January, 1 for Feb etc. until December, which is 11

Question 12

What’s the code that returns the year from a Date object “d”?

Answer 12

d.getFullYear();

Question 13

What’s the code to return the smallest unit of time that JavaScript recognizes from a Date object “d”?

Answer 13

d.getMilliseconds()

Question 14

Before you can getDate, getHours, or getFullYear, what must you do?

Answer 14

Get a Date object:
var d = new Date();

Question 15

What is the code to return the hour from a Date object “d”?

Answer 15

d.getHours();

*Note that HOURS is plural. MINUTES, SECONDS, and MILLISECONDS

Question 16

What is tricky about returning getMonth() from a Date object?

Answer 16

The numbers are off because the counting starts at zero. So January is zero and December is 11.

Question 17

What is tricky about returning getDate() from a Date object?

Answer 17

The count starts at 1, not zero.
This is different from all of the other Date object parts, like MONTH, HOURS, etc.

Question 18

How do you create a Date object for a time that is not right now?

Answer 18

new Date(“date info here”);

*The date should be in this format:
“June 30, 2024 13:10:53”

Question 19

Code a single statement that displays the milliseconds that elapsed between the reference date and the beginning of 1980.

Answer 19

new Date(“January 1, 1980”).getTime();

Question 20

What does “d” mean?
var d = new Date(“January 31, 2023”).getTime();

Answer 20

d is the number of milliseconds from the reference date (Jan 1, 1970) through Jan 31, 2023.