function Person(name) {
this.name = name;
}
Person.prototype.saySomething = function() {
return 'say Something!';
}
let john = new Person('john');
//john {name: 'john', saySomething: function}
newObj = Object.assign(Object.create(john))
newObj is an empty {} with the john properties as a prototype. How does that differ from just doing newObj = Object.create(john); ?
Object.assign is only useful when you provide more than one argument to it. It always returns the first argument it gets, which will be mutated by the other arguments. If you just provide one argument, there is no mutation happening, and so it is a no-operation really*.
Object.assign is sometimes called to populate a new object, created on-the-fly with {}, and then you see that this object is not a Person object:
function Person(name) {
this.name = name;
}
Person.prototype.saySomething = function() {
return 'say Something!';
}
let john = new Person('john');
//john {name: 'john', saySomething: function}
let created = Object.create(john);
let newObj = Object.assign({}, created);
console.log(created instanceof Person); // true
console.log(newObj instanceof Person); // false* There is a border case where Object.assign still makes a difference when called with just one argument: that is when you pass it a primitive value. In that case it will act like the Object function, wrapping the primitive into an object.
Object.assignwith just one argument is indeed a useless call.