Javascript Thinkful

Front 1

open Javascript Console in Chrome

Back 1

Option + Command + J on a Mac

Front 2

What does REPL stand for and what does a REPL do?

Back 2

REPL stands for read, evaluate, print loop. A REPL lets you type in code and evaluate it on the fly, basically letting you watch your code execute as you type.

Front 3

Write a statement that evaluates to the number 22 in the console.

Back 3

20 + 2

Front 4

What would the string “i’m a string” evaluate to in the console?

Back 4

“i’m a string”

Front 5

What is string concatenation? Give an example.

Back 5

String concatenation is combining two or more strings into a single string.

For example: “Hello ” + “ World” = “Hello World”

Front 6

How can you access previous commands in the console?

Back 6

Press the up key.

Front 7

What does the .alert() function do?

Back 7

The alert function opens up a pop-up box with whatever text you pass to it.

Front 8

What does .prompt() do?

Back 8

The prompt function opens up a pop up box with a text field that allows the user to type an answer, which it will then return to your code.

Front 9

What are the seven data types in JavaScript?

Back 9

Numbers, Strings, Boolean, Objects, Functions, Null and Undefined.

Front 10

What is the difference between null and undefined?

Back 10

Undefined means that a variable does not yet have a value, while null means that a variable has no value whatsoever.

Front 11

Enter an expression in the console that evaluates to NaN.

Back 11

parseInt(“Hello”);

Front 12

How can you determine the type of a value in JavaScript?

Back 12

The typeof operator.

typeof 15

typeof “cats”

typeof alert

typeof 15/”cats”

Front 13

>

Back 13

greater than

Front 14

<

Back 14

Less than

Front 15

==

Back 15

equality (converts the operands if they are not of the same type, then applies strict comparison)

Front 16

===

Back 16

strict equality (if two operands are strictly equal without type conversion)

Front 17

!=

Back 17

not equals

Front 18

!==

Back 18

strict not equals (if two operands are strictly not equal without type conversion)

Front 19

>=

Back 19

greater or equal

Front 20

<=

Back 20

less or equal

Front 21

(*)

Back 21

multiplication

Front 22

(/)

Back 22

division

Front 23

(+)

Back 23

addition

Front 24

(-)

Back 24

substraction

Front 25

(%)

Back 25

modulus

Front 26

What is the % operator called and what does it do?

Back 26

The % operator is the modulus operator in JavaScript and it returns the remainder from dividing the two arguments.

5 % 2 = 1

(5 / 2 = 4)

(5 - 4 = 1) remainder is 1

Front 27

What is the order of arithmetic operations in JavaScript

Back 27

PEMDAS

Parenthesis, Exponents, Multiplication, Division, Addition, then Subtraction.

Front 28

What is string concatenation and how do you do it?

Back 28

String concatenation combines two strings together. String concatenation is accomplished with the + operator with two strings as arguments.

Front 29

What happens if you concatenate a string and a number?

Back 29

The number is converted to its string equivalent and then regular string concatenation occurs.

EX: “Hi” + 1 = “Hi1”

Front 30

What does it mean to “escape” a character? Give some examples of escaped sequences in JavaScript.

Back 30

The backslash escape character turns special characters into string characters:

examples are: \n, the newline character, \, the backslash escape character, and \t, the tab character, to name a few.

Front 31

How can you quickly determine the length of a string?

Back 31

Apply the length property on the string.

hello = 'Hello World';

console.log(hello.length);

Front 32

Declare a variable whose name is car and assign your favourite car to it.

Back 32

var car = "Skoda"

Front 33

Find the length of the following sentence without manually counting the characters and spaces:

var sentence = "Please use the Contact us facility if you have any further issues or to report this e-mail as suspicious"

Back 33

sentence.length

Front 34

Let’s say we start with an empty parking lot. In the morning, people go to their jobs and want to secure their parking spot. Declare a variable called numCars and set its value to 0. Then, increment the variable by seventy, but without using the variables name twice in the new statement.

Back 34

var numCars = 0; numCars += 70;

Front 35

When the cars get into the parking lot, the car count is reported to the central controlling unit of the parking lot. Build a string called carCounterMessage that uses numCars to say: "There are now 70 cars in the parking lot!" You should not hardcode any value.

Back 35

var numCars = 0; numCars += 70; var carCounterMessage = "There are now " + numCars + " in the parking lot!"