Intro to JS

Question 1

Declare two variables: admin and name.
Assign the value “John” to name.
Copy the value from name to admin.
Show the value of admin using alert (must output “John”).

Answer 1

let admin, name; // can declare two variables at once

name = “John”;

admin = name;

alert( admin ); // “John”

Question 2

let

Answer 2

is a modern variable declaration

Question 3

var

Answer 3

is an old-school variable declaration. Normally we don’t use it at all, but has subtle differences from let

Question 4

const

Answer 4

is like let, but the value of the variable can’t be changed

Question 5

What are these called? ``

Answer 5

Backticks

Question 6

assignment operator

Answer 6

You can assign a value using the assignment operator =. For example:

let hello = “Hello”;

Question 7

7 primitive data types in JavaScript

Answer 7

String
Null
Undefined
Boolean
Number
BigInt
Symbol

Question 8

String

Answer 8

a string represents a sequence of characters and can be enclosed in either single (‘) or double (“) quotes.

Note that strings are immutable, which means once they are created, they cannot be changed.

Question 9

array

Answer 9

An array is a non-primitive data type that can hold a series of values.

Arrays are denoted using square brackets ([]). Here is an example of a variable with the value of an empty array:

let array = [];

Question 10

Primitive Data Type

Answer 10

Primitive data types like strings and numbers can only hold one value at a time.

Question 11

Non-Primitive Data Type

Answer 11

Non-primitive data types differ from primitive data types in that they can hold more complex data.

Question 12

Declare a variable

Question 13

Index

Answer 13

You can access the values inside an array using the index of the value. An index is a number representing the position of the value in the array, starting from 0 for the first value.

Question 14

How would you console log the first item in an array?

Answer 14

console.log(arrayName[0]);

Question 15

Mutable Arrays

Answer 15

Arrays are special in that they are considered mutable. This means you can change the value at an index directly.

For example, this code would assign the number 25 to the second element in the array:

let array = [1, 2, 3];
array[1] = 25;

Question 16

Use the .length array to get the last value of an array

Answer 16

array[array.length - 1]

Question 17

Method

Answer 17

A method in JavaScript is a function that’s associated with certain values or objects. An example you’ve already encountered is the .log() method, which is part of the console object.

Question 18

Array .push()

Answer 18

This allows you to “push” a value to the end of an array.
arrayName.push(12);

Question 19

Array .pop()

Answer 19

It removes the last element from an array and returns that element
popped = rows.pop();

Question 20

” “ or ‘ ‘

Answer 20

Generally, it doesn’t matter, but you want to be consistent throughout the build

Question 21

Const vs. Let

Answer 21

The let keyword allows a variable to be reassigned. This means you could change character later to be a completely different value.

First, a const variable cannot be reassigned like a let variable. This code would throw an error:

const firstName = “Naomi”;
firstName = “Jessica”;

A const variable also cannot be uninitialized. This code would throw an error:

const firstName;

Question 22

Iterator

Answer 22

The iterator is a variable you can declare specifically in your for loop to control how the loop iterates or goes through your logic.

It is a common convention to use i as your iterator variable in a loop.

Question 23

for loop syntax

Answer 23

for (let i = 0; i < count; i = i + 1) {
}

Question 24

concatenation