Does Object.assign() create a deep copy or a shallow copy?

I just came across this concept of

var copy = Object.assign({}, originalObject);

which creates a copy of original object into the "copy" object. However, my question is, does this way of cloning object create a deep copy or a shallow copy?

PS: The confusion is, if it creates a deep copy, then it would be the easiest way to clone an object.

Forget about deep copy, even shallow copy isn't safe, if the object you're copying has a property with enumerable attribute set to false.

MDN :

The Object.assign() method only copies enumerable and own properties from a source object to a target object

take this example

var o = {};

Object.defineProperty(o,'x',{enumerable: false,value : 15});

var ob={}; 
Object.assign(ob,o);

console.log(o.x); // 15
console.log(ob.x); // undefined