Variables & Types

Question 1

What is a template literal?

Answer 1

string literals allowing embedded expressions

i.e. string text ${expression} string text

Question 2

What does string.raw() do?

Answer 2

It takes the complete string of a template literal and renders it raw, including any escaped or special characters.

Question 3

What is the difference between let and const?

Answer 3

• Both are block scoped and you will receive a ReferenceError when accessing a variable before it’s declared
• Let can be reassigned while const cannot

Question 4

What is the difference between let and var?

Answer 4

• let is block scoped while var is global / function scoped
• referencing var before it is defined will result in ‘undefined’
• referencing let before its defined with result in a ReferenceError.

Question 5

What is the startsWith() method?

Answer 5

• The startsWith() method determines whether a string begins with the characters of a specified string.
• Method is case sensitive
• Returns a boolean value.

string.startsWith (searchvalue, start) –> The start value is optional. If not specified, it starts at the beginning of the string. If specified, it will start at the index specified.

Example:

var str = “Hello world, welcome to the universe.”;

var n = str.startsWith(“world”, 6); returns true

Question 6

What is the ends with() method?

Answer 6

• Determines whether a string ends with the characters of a specified string.
• Case sensitive
• returns a boolean value

Syntax: string.endsWith(searchvalue, length)

where length is optional. It specified the length of the string to search from the start of the string.

var str = "Hello world, welcome to the universe.";
var n = str.endsWith("world", 11); **returns true**

Question 7

What is an example of a correct destructuring syntax for deconstructing an array?

Answer 7

var [Id, ApplicantName] = arr;

Question 8

T/F: A template literal always has more strings than values

Answer 8

True

Question 9

What is a Symbol in JavaScript?

Answer 9

• primitive data type
• the Symbol() function returns a value of type symbol
• A symbol value may be used as an identifier for object properties
• A globally unique, un-guessable value

Question 10

What does Number.isSafeInteger(value) do?

Answer 10

Test if the value is and integer and falls between MIN_SAFE_INTEGER and MAX_SAFE_INTEGER