how to add items in constant object in javascript code example

Example 1: adding element to javascript object

let person = {
  name : 'John Doe',
  age : 35
}

//Now we can add element by 2 ways
person.occupation = 'Web Designer'
//or
person['occupation'] = 'Web Designer'; //This is usefull for adding element within loop.

object[yourKey] = yourValue;
object.yourKey = yourValue;

Example 2: 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.