what is const variable in javascript code example
Example 1: what is const in javascript
const age; // errror as const cannot be kept un-initialized;
const age = 20 ;
const age = 21 , // error as once declared const variable cann't be
// re-declared in same scope or different scope.
Example 2: const in javascript
const value = 10;
const constant = value;
Example 3: var or const in javascript
// var declares a variable, meaning its value will vary.
// const declares a constant, meaning its value will remain
// consistant and not change.
// If your variable changes throughout the program or website,
// declare it using a var statement.
// Otherwise, if its value does not change, declare it using
// a const statement.
const myConst='A const does not change.';
var myVar='A var does change.';
var myVar=2;
Example 4: js define constant by element id
const elem = document.getElementById('elementID');
Example 5: const {} = object in javascript
/*The destructuring assignment syntax is a JavaScript expression that
makes it possible to unpack values from arrays, or properties from objects,
into distinct variables.*/
let array = [2,3];
[a,b] = array;// unpacking array into var a and b
console.log(a); //output 2
console.log(b); //output 3
let object = {name:"someone",weight:"500pounds"};
let {name,weight} = object; // unpacking object into var name and weight
console.log(name);// output someone
console.log(weight);//output 500pounds
//it i similar as doing this
/*
var a = array[0];
var b = array[1]
var name = object.name;
var weight = object.weight;
*/