Javascript

Front 1

What are primitives?

Back 1

Primitives are values, they have no properties. A primitive can be referenced by a property.

A primitive can be referenced by a property.

A primitive can be referenced by a property.

Front 2

What are the types of primitives?

Back 2

Undefined, null, boolean, string and number

Front 3

What is garbage collection?

Back 3

The automatic process by which JavaScript clears blocks of memory for data that is no longer in use.

Front 4

What are the types of objects?

Back 4

Math

Date

JSON

window

Document

Objects the programmer creates

Array

Function

Sometimes primitives are objects too (numbers, booleans, strings) when a property or method is called on it it is temporarily converted to an object to return a value, it is then converted back to a primitive.

Basically everything in JavaScript is an object

Front 5

What is an object?

Back 5

An object is a collection of properties and a property is an association between a name (or key) and a value. A properties value can be a function in which case the property is known as a method.

Front 6

What is a method?

Back 6

A properties value can be a function, in which case the property if known as a method.

Front 7

What is immutability?

Back 7

An immutable value is one which cannot be changed. Examples include strings and numbers, they cannot be changed, only new strings and numbers can be created.

Front 8

What is event binding?

Back 8

Event binding refers to telling the browser that a particular function should be called whenever some event occurs.

Front 9

What is const?

Back 9

Const is a variable which cannot be rebinded. Once you bind a value/object to a const variable you can't reassign to that variable.

const something = {};

something = 10; //error

let somethingElse = {};

somethingElse = 1000; //this is fine

const does not make something immutable.

const myArray = [];

myArray.push(10)//this works fine.

Front 10

What is let?

Back 10

In es6 let is basically the new car but has a new kind of scope called block scoping. Unlike const, let can be binded to a new data type after being created.

Front 11

What is the || operator?

Back 11

Is a logical operator. It means or. When used in an if statement with boolean values, if either operand (a || b) is true it evaluates to true. If both are false it is false.

|| Returns the value of one of the specified operands. If the first is false, the second will be returned. If it is a non boolean value, it will return the value as it is.

Front 12

What if the && operator?

Back 12

A logical operator. Returns true if both a && b are true.

If a is false it will return the value of b. If used with non boolean values it will return whatever the value is.

Front 13

What is the ! Operator?

Back 13

It is a logical operator. Returns false if it's operand can be converted to true and returns true if it's operand can be converted to false.

const a = false;

!a = true;

a = true;

a = false;

!a = true;

Front 14

What is block scoping?

Back 14

Block scoping is when a variable is available within the block it's created in and isn't hoisted to the function it's a part of. 'let' allows block scoping while 'var' is hoisted to the scope if the function it's in and not the block.