var and const 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: javascript const

const b = 1; // this variable unique and can't change it.

Example 4: 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 5: js define constant by element id

const elem = document.getElementById('elementID');

Example 6: const js +=

const foo; // Errror as const cannot be kept un-initialized;
const foo = "foo";
console.log(foo); //Output: foo
foo += " bar"; //Error