Considering following code:
var obj1 = Object.create({}, {myProp: {value: 1}}); var obj2 = Object.assign({}, {myProp: 1});
Is there any difference between obj1
and obj2
since each object has been created in a different way?
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Answer
Let’s compare obj1
and obj2
in this code:
var target1 = {}, target2 = {}; var obj1 = Object.create(target1, {myProp: {value: 1}}); var obj2 = Object.assign(target2, {myProp: 1});
Prototypical chain
Object.create
creates a new object with the specified [[Prototype]], and Object.assign
assigns the properties directly on the specified object:
obj1 !== target1; obj2 === target2;
The prototypical chains of obj1
and obj2
look like
obj1 --> target1 --> Object.prototype --> null obj2 --------------> Object.prototype --> null
Properties
Object.create
defines properties and Object.assign
only assigns them.
When creating a property, assignments will create it as configurable, writable and enumerable. When defining a property, you can specify those flags, but by default it’s not configurable, nor writable and not enumerable.
Object.getOwnPropertyDescriptor(obj1, 'myProp'); // { value: 1, writable: false, enumerable: false, configurable: false } Object.getOwnPropertyDescriptor(obj2, 'myProp'); // { value: 1, writable: true, enumerable: true, configurable: true }