how to use the value of a variable in javascript code example

Example 1: how to define variable in javascript

var <variable-name>;

var <variable-name> = <value>;

Example 2: variable in js

////We can define variables in 3 ways {var,let,const}/////// 
////syntax- var variable_name=value;
/////  let variable_name=value;
/////const variable_name=value;

var myfristvariable="neha jaiswal";
const mysecondvariable=80;
let mythirdvar=abc;