add key value pair to an object javascript code example

Example 1: javascript add to object

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

// Array of Objects in form {element: {id: 10, quantity: 10} }
var element = {}, cart = [];
element.id = id;
element.quantity = quantity;
cart.push({element: element});

Example 2: add new key value pair to object javascript

const person = {
	name: "Elon Musk"
}

person.age = 49;

console.log(person);
// {name: "Elon Musk", age: 49}