how to add property to the back of an object code example
Example: add key vakue to front of object
let obj = {'b': 2, 'c': 3};
Object.assign({a: 1}, obj);
// Object {a: 1, b: 2, c: 3}
let obj = {'b': 2, 'c': 3};
Object.assign({a: 1}, obj);
// Object {a: 1, b: 2, c: 3}