ES6

Question 1

What kind of typed language is JavaScript?

Answer 1

JavaScript is a dynamically typed language. The type of variable is infered from the value assigned to it.

Question 2

What exactly are variables?

Answer 2

Boxes or containers for storing data. They are named containers and you can use the name to retrieve the value later.

Var, Let, Const

Question 3

What is interpolation? How to do it in ES6?

Answer 3

You use backticks and also ${variableName}

Question 4

What is let?

Answer 4

Let is very similar to var with the exception that the variable can not be redeclared after declaration var is also scoped to the nearest ‘function block’

Let is scoped to the nearest ‘enclosing block’ - which can be a smaller scope than a function block.

Question 5

What is an escape character?

Answer 5

It’s a \ in JavaScript that indicates that the next character should not be read.

Question 6

What are operators?

Answer 6

Operators are used to assign values, compare values, perform arithmetic operations and more.

Ternary, binary, unary

Ternary:

condition ? expr1 : expr2

Binary:

1 + 2

Unary Operators

a++

++a

Question 7

What does a switch statement do? How about a do-while loop?

Answer 7

color = ‘red’;

switch(red){

color ‘green’:

console…break

default:

}

Question 8

What is the purpose of a function?

Answer 8

Functions let you group a series of statement together to perform some task. Once a function is created, it can be reused over and over in your code. If you find yourself repeating statement in your code, then a function may be the answer to avoid that repetition. DRY - Don’t Repeat Yourself

Functions in javascirpt are first class objects…They can have properties and methods just like any other object. Where they DIFFERE< is in the fact that functions can be called

Question 9

Explain hoisting in JavaScript

Answer 9

Declared (not assigned) variables are sent to the top. So are functions

Question 10

How do you call an anonymous function?

Answer 10

let sayGreeting = function(){}

sayGreeting();

Question 11

What is an IIFE?

Answer 11

Immediately Invoked Function Expression

A way to immediately run the function when the pointer/variable is called. So, you have

Question 12

What is a fat arrow function?

Answer 12

1) () =>
2) one return statement, no code blocks
3) one parameter, no need to use ()
4) no need to type function

Question 13

Explain the ‘this’ keyword

Answer 13

In JS, the thing called this, is the objec that ‘owns’ the JS code

The value of this, when used in a fucntion, is the objec that ‘owns’ the function

The value of this, when used in an object, is the object itself

Question 14

What is an object? What are two ways to construct?

Answer 14

It is a value type that contains key value pairs inside {}

Keys are also known as properties

Everything that isn’t a primitive type is an object

Question 15

What are some basic methods for an Array?

Answer 15

Pop, push, shift, unshift, concat, reverse, sort (remember you can put condition), slice (remember, slice does not include the last part of the argument,,,2,5 doesn’t not include 5

Question 16

What are some ES6 array helpers?

Answer 16

You can use, forEach, like a for loop

You can also use toFixed (1)…fixes the decimal to just 1

Map, takes an array, you can return manipulations on the array values and then return a new arrayu

Filter - Which can return values only based on a condition

Find -