Variables In JS

What are we going to learn in this video?

  • What are variables?
  • What are different data types in JS?
  • What is typeof operator

What are variables??

Variables are the one which holds a value and that value can be changed and used in other places.

Here one is the variable name and 1 is the value it holds.

var one = 1;

one = "one";

In What is JS video, I said that JS is a weakly typed variable. What that means is, in the above statement, variable is assigned a value of data type of number and in run time 1 is replaced by "one" which is completely different data type(string).

 

Many of the languages won’t allow this but JS since it is dynamic and weakly typed it allows it.

Data Types

There are two broad types of data types in JS,

 

1. Primitive

  • Number
  • String
  • Boolean
  • null
  • undefined

2. Non Primitive

  • Objects
  • Array

Const and let

Till ES5, there was no block level scope in Javascript,

 

What is block level scope??

 

if {
// This is a block

}

for () {

//This is a block
}

Const and let are created in ES6 to support block level scope.

Typeof

Type of is one of an operator in Javascript. Typeof is used to find the type of the variable.

const city = 'bengaluru';

typeof city // string

const num = 1000;

typeof num // number

const isValid = true;

typeof isValid // boolean

Variables

By hentry martin

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Variables

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