Javascript

What is javascript

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What is javascript

JavaScript is a scripting or programming language that allows you to implement complex features on web pages — every time a web page does more than just sit there and display static information for you to look at — displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. — you can bet that JavaScript is probably involved. It is the third layer of the layer cake of standard web technologies, two of which (HTML and CSS) we have covered in much more detail in other parts of the Learning Area.

JavaScript Variables

Variables are Containers for Storing Data

JavaScript Variables can be declared in 4 ways:

1)Automatically

2)Using var

3)Using let

4)Using const

When to Use var, let, or const?

1. Always declare variables

2. Always use const if the value should not be changed

3. Always use const if the type should not be changed (Arrays and Objects)

4. Only use let if you can't use const

5. Only use var if you MUST support old browsers.

Js output

<script>

    var a = 10;

    console.log(a);

    var a = "Satish";

    console.log(a)

    Types of variable

    var,let,const

    b = 20;

    var b = 60;

    let c= 30;

    console.log(c)

    c= 45;

    console.log(c)

    const d = 66;

    console.log(d)

   // d = 68;

    console.log(d)

</script>

Differences between var, let, and const

‘use strict’;

This keyword is used to strictly follow the variable declaration before using it

Eg:-

'use strict';

x= 10;

console.log(x);

Error will be  ReferenceError: x is not defined  

Variable Hoisting

It means a variable will not be used before declaration

x= 10;

console.log(x);

let x;