why we use local storage in javascript code example

Example 1: local storage javascript

function createItem() {
	localStorage.setItem('nameOfItem', 'value'); 
} 
createItem() // Creates a item named 'nameOfItem' and stores a value of 'value'

function getValue() {
	return localStorage.getItem('nameOfItem');  
} // Gets the value of 'nameOfItem' and returns it
console.log(getValue()); //'value';

Example 2: javascript localstorage

var KeyName = window.localStorage.key(index);