JavaScript

Question 1

Front-End vs. Back-End Programming

Answer 1

Front-End

• Writing code that runs in the browser
• Faster to respond to user interaction

Back-End

• Writing code that runs on the server
• Slower to respond to user interaction
• Can be used for more than just user interaction

Question 2

Where does the code written during front-end programming run?

Answer 2

The broswer

Question 3

Where does the code written during back-end programming run?

Answer 3

The server

Question 4

What are arrays used for?

Answer 4

Arrays are used to store multiple values in a single variable

An ordered collection of values
Each value is called an element
Each element has a numeric position in the array that is know as its index
Indexes are zero-based

Question 5

JavaScript Types

Answer 5

Primitive Types - numbers, strings, booleans, null, undefined

Object Types - can apply to anything that’s not a primative type - collection of Keys and Values

Question 6

what does array.push(“”) do?

Answer 6

Adds a element to the end of an array

Question 7

what does array.pop(“”) do?

Answer 7

deletes an element from an array

Question 8

what does array.concat(array2) do?

Answer 8

adds array and array2 together

Question 9

Implicit Type Conversion

Answer 9

Performed automatically by JavaScript
11 + “ “ //output: “11” (number 11 converts to string “11”)
“15” + 15 //output: “1515” (concatenates “15” and 15 into a string)
“10” - “5”//output 5 (both strings convert to numbers)

Question 10

Explicit Type Conversion

Answer 10

Performed explicitly in code:
String(25)//Output: “25” (number 25 converts to a string)
Number(“25”)//Output: 25 (string “25” converts to a number)

Question 11

What are the three ways to declare a variable and how do they differ?

Answer 11

• var - globally scoped. define the variable outside of a function, can be declared and redeclared
• let - block scoped. must be defined within { } - can be updated but not redeclared
• const - cannot be updated or redeclared - constant

Question 12

Expression vs. Statement

Answer 12

An expression is any code that can evaluate to a value

A statement is an instruction to do a certain action

Question 13

Loose vs Strict Equality

Answer 13

Loose ==
Checks if two operands are equal (tries to convert the values to a common type before checking for equality)

Strict ===
Checks if two operands are equal (checks if the types are equal as well)

Question 14

Iteration

Answer 14

Repeating a process (lines of code)

Helpful for processing every element in an array

Question 15

The three clauses of a For Loop

Answer 15

1. Initializer - runs before the loop
2. Condition - a boolean expression that stops the loop when it’s false
3. Afterthought - runs at the end of each cycle of the loop

Question 16

While Loops

Answer 16

Will execute a code block as long as the desired condition is true

Question 17

Parts of a function

Answer 17

• Function keyword
• Function name
• Parentheses
• Function body

Question 18

How do you invoke a function

Answer 18

Function name
Parenthesis

functionName()

Functions can be used multiple times

Question 19

Parameters and Arguments

Answer 19

Parameters and arguments allow you to make functions that are more generic, using variables that can have different values each time the function runs

Question 20

How are parameters formatted

Answer 20

• Variable inputs for a function
• Listed where a function is defined
• between the parentheses
• separated by commas

Question 21

How are Arguments Formatted?

Answer 21

• Listed where a function is invoked
• Between parentheses
• Separated by commas