Strings

Question 1

What are some examples of String literals?

Answer 1

‘String text’
“String text”
“Charactersinanylanguage”

Question 2

How would you create a string using the String global object directly?

Answer 2

String(thing)

Parameters:

thing - anything to be converted to a string.

Question 3

Since ECMAScript 2015, what can string literals be called?

Answer 3

Template strings

Question 4

What is Escape notation and why use it?

Answer 4

Escape notation: \

Beside regular, printable characters, special characters can be encoded using escape notation.

Ex: \n for a new line. ' for a single quote

Question 5

Does JavaScript differentiate between single quotes(‘’) and double quotes(“”)?

Answer 5

JavaScript makes no distinction between single or double quotes.

Question 6

What two ways can you combine long literal strings, such as this question, to keep from having lines that go on endlessly?

You would use these techniques to make your code more readable.

Answer 6

Either use the + operator or a \ at the end of each line. The \ cannot have any spaces immediately after it.

Ex1: “What two ways can you combine long “ + “literal strings, such as this question, to “…”;

Ex2: “What two ways can you combine long \
literal strings, such as this question, to \ …”;

Question 7

What are strings most useful for?

Answer 7

Strings are most useful for holding data that can be represented in text form.

Question 8

You can use the operators + and += on strings?

Answer 8

True.

Question 9

What are the two ways to access an individual character in a string?

Answer 9

charAt()

Ex: return ‘cat’.charAt(1); // returns “a”

‘someString’[1]

Ex: return ‘cat’[1]; // returns “a”

Question 10

What is a String?

Answer 10

The String global object is a constructor for strings, or a sequence of characters.

Question 11

What is the most common way to compare strings?

Answer 11

Using the less than operators.

Less common option but still valid:
A similar result can be achieved using the localeCompare() method inherited by String instances.

Question 12

What does localeCompare() method do? and what is its syntax?

Answer 12

The localeCompare() method returns a number indicating whether a reference string comes before or after or is the same as the given string in sort order.

Syntax:
referenceStr.localeCompare(compareString[, locales[, options]])

Example:
// The letter “a” is before “c” yielding a negative value
‘a’.localeCompare(‘c’); // -2 or -1

Question 13

True / False:

JavaScript distinguishes between String objects and primitive string values.

Answer 13

True

Question 14

What are string primitives?

Answer 14

String literals (denoted by double or single quotes) and strings returned from String calls in a non-constructor context (i.e., without using the new keyword) are primitive

Question 15

True / False:

JavaScript does not automatically converts primitives to String objects, so that it’s possible to use String object methods for primitive strings

Answer 15

False

In contexts where a method is to be invoked on a primitive string or a property lookup occurs, JavaScript will automatically wrap the string primitive and call the method or perform the property lookup.

Question 16

How do you convert a String Object to its primitive counterpart?

Answer 16

A String object can always be converted to its primitive counterpart with the valueOf() method.

Question 17

How would you add a property to the String Object?

Answer 17

String.prototype

Allows the addition of properties to a String object.

Question 18

What does the method String.formCharCode() do? And What is an example?

Answer 18

String.fromCharCode():

Returns a string created by using the specified sequence of Unicode values.

Example:
String.fromCharCode(65); // “A”

Question 19

What does the property String.prototype.length do? And what is an example?

Answer 19

String.prototype.length
Reflects the length of the string.

Example:
‘String’.length; // 6

Question 20

What does the method String.prototype.charAt() do? And What is an example?

Answer 20

String.prototype.charAt():
Returns the character at the specified index.

Example:
‘String’.charAt(4); // ‘n’

Question 21

What does the method String.prototype.charCodeAt() do? And What is an example?

Answer 21

String.prototype.charCodeAt():
Returns a number indicating the Unicode value of the character at the given index.

Example:
‘String’.charCodeAt(2); // 114 (unicode value of r)

Question 22

What does the method String.prototype.concat() do? And What is an example?

Answer 22

String.prototype.concat():
Combines the text of two strings and returns a new string.

Example:
‘String’.concat(‘ love’); // ‘String love’

Question 23

What does the method String.prototype.includes() do? And What is an example?

Answer 23

String.prototype.includes():
Determines whether one string may be found within another string.

Example:
‘String’.includes(‘ring’); // true
‘Blue Whale’.includes(‘blue’); // false

Question 24

What does the method String.prototype.endsWith() do? And What is an example?

Answer 24

String.prototype.endsWith():
Determines whether a string ends with the characters of another string.

Example:
‘String’.endsWith(‘ng’); // true
‘String’.endsWith(‘ri’); // false

Question 25

What does the method String.prototype.indexOf() do? And What is an example?

Answer 25

String.prototype.indexOf():
Returns the index within the calling String object of the first occurrence of the specified value, or -1 if not found.

Example:
‘Blue Whale’.indexOf(‘Blue’); // returns 0

Question 26

What does the method String.prototype.lastIndexOf() do? And What is an example?

Answer 26

String.prototype.lastIndexOf():
Returns the index within the calling String object of the last occurrence of the specified value, or -1 if not found.

Example:
‘canal’.lastIndexOf(‘a’); // returns 3

Question 27

What does the method String.prototype.match() do? And What is an example?

Answer 27

String.prototype.match():
Used to match a regular expression against a string.

Example:
var str = ‘ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstu’;
var regexp = /[A-E]/gi;
var matches_array = str.match(regexp);
console.log(matches_array); // [‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘a’, ‘b’, ‘c’, ‘d’, ‘e’]

Question 28

What does the method String.prototype.repeat() do? And What is an example?

Answer 28

String.prototype.repeat():
The repeat() method constructs and returns a new string which contains the specified number of copies of the string on which it was called, concatenated together.

Example:
‘abc’.repeat(1); // ‘abc’
‘abc’.repeat(2); // ‘abcabc’

Question 29

What does the method String.prototype.replace() do? And What is an example?

Answer 29

String.prototype.replace():
The replace() method returns a new string with some or all matches of a pattern replaced by a replacement. The pattern can be a string or a RegExp, and the replacement can be a string or a function to be called for each match.

Example:
var str = ‘Twas the night before Xmas…’;
var newstr = str.replace(/xmas/i, ‘Christmas’);
console.log(newstr); // Twas the night before Christmas…

Question 30

What does the method String.prototype.search() do? And What is an example?

Answer 30

String.prototype.search():
Executes the search for a match between a regular expression and a specified string.

Example:
‘string’.search(‘m’); // -1
‘string.search(‘n’); // 0

Question 31

What does the method String.prototype.slice() do? And What is an example?

Answer 31

String.prototype.slice():
Extracts a section of a string and returns a new string.

Example:
var str1 = ‘The morning is upon us.’;
var str2 = str1.slice(4, -2);
console.log(str2); // OUTPUT: morning is upon u

Question 32

What does the method String.prototype.split() do? And What is an example?

Answer 32

String.prototype.split():
Splits a String object into an array of strings by separating the string into substrings.

Example:
‘string’.split(‘r’); // [“st”, “ing”]
“abcabcabcabcabc”.split(‘c’, 2); // [“ab”, “ab”]

Question 33

What does the method String.prototype.startsWith() do? And What is an example?

Answer 33

String.prototype.startsWith():
Determines whether a string begins with the characters of another string.

Example:
//startswith
var str = 'To be, or not to be, that is the question.';

console. log(str.startsWith(‘To be’)); // true
console. log(str.startsWith(‘not to be’)); // false
console. log(str.startsWith(‘not to be’, 10)); // true

Question 34

What does the method String.prototype.substr() do? And What is an example?

Answer 34

String.prototype.substr():
Returns the characters in a string beginning at the specified location through the specified number of characters.

Example:
var str = 'abcdefghij';

console. log(‘(1, 2): ‘ + str.substr(1, 2)); // ‘(1, 2): bc’
console. log(‘(-3, 2): ‘ + str.substr(-3, 2)); // ‘(-3, 2): hi’

Question 35

What does the method String.prototype.substring() do? And What is an example?

Answer 35

String.prototype.substring():
Returns the characters in a string between two indexes into the string.

Example:
var anyString = 'Mozilla';

// Displays ‘Moz’

console. log(anyString.substring(0, 3));
console. log(anyString.substring(3, 0));

Question 36

What does the method String.prototype.toLowerCase() do? And What is an example?

Answer 36

String.prototype.toLowerCase():
Returns the calling string value converted to lower case.

Example:
‘STRING’.toLowerCase(); // ‘string’

Question 37

What does the method String.prototype.toString() do? And What is an example?

Answer 37

String.prototype.toString():
The String object overrides the toString() method of the Object object; it does not inherit Object.prototype.toString(). For String objects, the toString() method returns a string representation of the object and is the same as the String.prototype.valueOf() method.

Example:
var x = new String('Hello world');

console.log(x.toString()); // logs ‘Hello world’

Question 38

What does the method String.prototype.toUpperCase() do? And What is an example?

Answer 38

String.prototype.toUpperCase():
Returns the calling string value converted to uppercase.

Example:
‘alphabet’.toUpperCase(); // ‘ALPHABET’

Question 39

What does the method String.prototype.trim() do? And What is an example?

Answer 39

String.prototype.trim():
Trims whitespace from the beginning and end of the string. Part of the ECMAScript 5 standard.

Example:
var orig = ‘ foo ‘;
console.log(orig.trim()); // ‘foo’

Question 40

What does the method String.prototype.valueOf() do? And What is an example?

Answer 40

String.prototype.valueOf():
The valueOf() method of String returns the primitive value of a String object as a string data type. This value is equivalent to String.prototype.toString().

Example:
var x = new String(‘Hello world’);
console.log(x.valueOf()); // Displays ‘Hello world’