Basics

Question 1

What’s exponent operator?

Answer 1

**

Question 2

What’s the difference between == and ===?

Answer 2

Strict equality (no attempt at type conversion)

Question 3

What are the three methods for declaring strings?

Answer 3

’ ‘, “ “, ` `

Question 4

How do you add quotation marks inside a string?

Answer 4

with the \ (escape) character

Question 5

What are commonly used escape characters in strings?

Answer 5

Code	Output
\'	single quote
\"	double quote
\\	backslash
\n	newline
\r	carriage return
\t	tab
\b	word boundary
\f	form feed

Question 6

What does it mean to say string values are immutable?

Answer 6

They cannot be altered once created, only assigned a new string.

Not allowed:
var myStr = "Bob";
myStr[0] = "J";

Question 7

What is the scope of variables assigned without the var keyword?

Answer 7

global

Question 8

What happens when a local and global variable have the same name?

Answer 8

the local variable takes precedence

Question 9

What’s the syntax for a switch statement?

Answer 9

switch(lowercaseLetter) {
case "a":
console.log("A");
break;
case "b":
console.log("B");
break;
}

Question 10

How are case values in a switch statement evaluated?

Answer 10

with strict equality

Question 11

How do you execute a case in a switch statement if no matching values are found

Answer 11

with default

Question 12

What does break do in switch statements?

Answer 12

tell javascript to stop executing statements

Question 13

What’s the syntax for a switch statement that has multiple inputs with the same output?

Answer 13

switch(val) {
case 1:
case 2:
case 3:
result = "1, 2, or 3";
break;

Question 14

What are the two ways to access object properties?

Answer 14

There are two ways to access the properties of an object: dot notation (.) and bracket notation ([])

Question 15

What’s the syntax for declaring an object?

Answer 15

var myObj = {
prop1: "val1",
prop2: "val2"
};

Question 16

When would you use dot notation to access an objects properties?

Answer 16

When you know the key name and it has no spaces.

Question 17

What’s the syntax for accessing an object’s values when the key name has spaces?

Answer 17

myObj[“Space Name”]; // Kirk
myObj[‘More Space’]; // Spock
myObj[“NoSpace”]; // USS Enterprise
Note that property names with spaces in them must be in quotes (single or double).

Question 18

How do you access an object’s values when the key name is a variable?

Answer 18

With bracket notation and no quotes around the variable.

Question 19

What’s the syntax for deleting an object’s property?

Answer 19

delete ourDog.bark;

Question 20

What function checks if an object has a property?

Answer 20

.hasOwnProperty(propname)

Question 21

What’s the syntax for a while loop?

Answer 21

while(i < 5) {
ourArray.push(i);
i++;
}

Question 22

What’s the difference between a while and do..while loop?

Answer 22

A do…while loop executes the loop body at least once

Question 23

What’s the syntax for a do…while loop?

Answer 23

do {
ourArray.push(i);
i++;
} while (i < 5);

Question 24

What does Math.random() do?

Answer 24

generates a random decimal number between 0 (inclusive) and not quite up to 1 (exclusive). Thus Math.random() can return a 0 but never quite return a 1

Question 25

How do you generate random whole numbers?

Answer 25

Math.floor(Math.random() * 20);

Question 26

How do you generate random numbers between a maximum and minimum value?

Answer 26

Math.floor(Math.random() * (max - min + 1)) + min

Question 27

How do you convert a string to an integer?

Answer 27

var a = parseInt(“007”);

Question 28

How do you convert a string to a number of a different base?

Answer 28

var a = parseInt("11", 2);
The radix variable says that "11" is in the binary system, or base 2. This example converts the string "11" to an integer 3.

Question 29

What’s the syntax for a one line if-else expression?

Answer 29

condition ? expression-if-true : expression-if-false;

Question 30

What’s the syntax for a multi-line ternary operator?

Answer 30

function findGreaterOrEqual(a, b) {
return (a === b) ? "a and b are equal"
\: (a > b) ? "a is greater"
\: "b is greater";
}

Question 31

What’s the ES6 syntax for declaring functions?

Answer 31

let name = (num1, num2) => {
body
}

Question 32

What does a function without the return keyword return?

Answer 32

undefined

Question 33

What’s the ES5 syntax for a regular function?

Answer 33

function name(num1, num2) {
body
}

Question 34

What’s the ES5 syntax for an anonymous function?

Answer 34

let name = function(num1, num2) {
body
}

Question 35

What’s the syntax for looping through an object?

Answer 35

for (let key in obj) {
body
}

Question 36

How do you execute a function on each element of an array?

Answer 36

forEach()

Question 37

How do you combine all the elements of an array into a single string?

Answer 37

join()

Question 38

How do you find the index of a single element in an array?

Answer 38

indexOf()

Question 39

How do you extract a sequential part of an array?

Answer 39

arr.slice([start[, end]])

the resulting array will include the start, but not the end

Question 40

How do you change the contents of an array by removing or replacing existing elements?

Answer 40

.splice

let arrDeletedItems = arr.splice(start[, deleteCount[, item1[, item2[, …]]]])

Question 41

What does the splice function return?

Answer 41

the array of deleted elements

Question 42

How do execute a function on an array and return a new array?

Answer 42

The map() method creates a new array populated with the results of calling a provided function on every element in the calling array.

const map1 = array1.map(x => x * 2);