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;

//Consider the following example object literal:
var myObject = {
    sProp: 'some string value',
    numProp: 2,
    bProp: false
};

//You can use dot syntax to add a new property to it as follows:
myObject.prop2 = 'data here';

//Modify a Property of an Object Literal
//The process for modifying a property is essentially the same. 
//Here we will assign a new value to the sProp property shown in the 
//original myObject definition above:
myObject.sProp = 'A new string value for our original string property';

//Read Current Value of Object Property
//The following demonstrates how to access a property of an object literal:
alert(myObject.sProp) // display myObject.sProp value in alert
var val = myObject.sProp; // assign myObject.sProp to variable

var element = {};
element.push({ id: id, quantity: quantity });
cart.push(element);