JS week 1 day 1

Question 1

What is the purpose of variables?

Answer 1

variable stores the data value that can be changed later on

Question 2

How do you declare a variable?

Answer 2

use keyword var, let or const

Question 3

How do you initialize (assign a value to) a variable?

Answer 3

by using = operator

Question 4

What characters are allowed in variable names?

Answer 4

letters, underscore, dollar sign, subsequent characters can be numbers, no spaces

Question 5

What does it mean to say that variable names are “case sensitive”?

Answer 5

if variable names include same letters but one cases do not match, strings values do not equate to each other

Question 6

What is the purpose of a string?

Answer 6

JavaScript strings are used for storing and manipulating text.

Question 7

What is the purpose of a number?

Answer 7

to perform arithmetic operations, and describe/store numeric values.

Question 8

What is the purpose of a boolean?

Answer 8

Booleans are used as functions to get the values of variables, objects, conditions, and expressions. true/false

Question 9

What does the = operator mean in JavaScript?

Answer 9

assignment operator

Question 10

How do you update the value of a variable?

Answer 10

remove the declaration key word, variable name = “different value”

Question 11

What is the difference between null and undefined?

Answer 11

undefined means a variable has been declared but has not yet been assigned a value. null is an assignment value but can be assigned to a variable as a representation of no value. ( null = intentional absence of value)

Question 12

Why is it a good habit to include “labels” when you log values to the browser console?

Answer 12

to help debug

Question 13

Give five examples of JavaScript primitives.

Answer 13

string, number, boolean, null, undefined

Question 14

What data type is returned by an arithmetic operation?

Answer 14

number

Question 15

What is string concatenation?

Answer 15

appends one string to the end of another string

Question 16

What purpose(s) does the + plus operator serve in JavaScript?

Answer 16

addition operator

Question 17

What data type is returned by comparing two values (, ===, etc)?

Answer 17

boolean

Question 18

What does the += “plus-equals” operator do?

Answer 18

The addition assignment operator ( += ) adds the value of the right operand to a variable and assigns the result to the variable.

Question 19

What are objects used for?

Answer 19

to group together a set of variables and functions to create a model of something. In JavaScript, almost “everything” is an object.

Question 20

What are object properties?

Answer 20

Properties are the values associated with a JavaScript object. (If a variable is part of an object, it is called properties)

Question 21

What are the two ways to get or update the value of a property?

Answer 21

using dot or bracket notation

Question 22

Describe object literal notation.

Answer 22

curly braces assigned to variable.

Question 23

How do you remove a property from an object?

Answer 23

delete operator

Question 24

What are arrays used for?

Answer 24

arrays are used to store list of values.

Question 25

What number represents the first index of an array?

Answer 25

0

Question 26

How are arrays different from “plain” objects?

Answer 26

objects are used to store collection of data and arrays are used to store list of values. arrays are numerically indexed and objects are not ordered.

Question 27

What is the length property of an array?

Answer 27

length property returns number of elements in an array.