Object.create() in Javascript

March 21st, 2020
3 mins read

by Dillion Megida

Category: JAVASCRIPT

#javascript

Maximum of 20 articles can be saved!

Object.create() in Javascript

March 21st, 2020
3 mins read

by Dillion Megida

Category: JAVASCRIPT

#javascript

Maximum of 20 articles can be saved!

Object.create() is a javascript method (function on an object) that creates a new object while using a former object as the new object's prototype.

What are prototypes?

Prototypes are also objects. For an object (A) to be a protoype of object (B), it means that B has access to some properties of A. Look at it like, B was built on top of A. An example is the global Object, which is a prototype of all objects created. For example:

let obj = {
    name: 'Object',
    number: 3,
    print: function() {
        return 'A method, yeah'
    }
}
console.log(
    obj.name,
    obj.number,
    object.print()
)
// Expected output
// Object
// 3
// A method, yeah

As we can see in the object above, there are only two properties and one method.

But, the following would also work:

console.log(
    obj.hasOwnProperty('name');
    obj.hasOwnProperty('type');
)
// Expected output
// true
// false

Where does hasOwnProperty method come from?

Well, from the global Object which is a prototype of obj. To check this out, try this:

console.log(obj);

In the console, you'll find the properties and method logged, but with one faded (hidden) property - __proto__. When you view more about the property, you'll find the constructor Object which has the hasOwnProperty method. That's basically what prototypes are.

Object.create() in action

Syntax

Object.create() is a method which takes an argument of the object which would be the prototype of the new object.

const newObj = Object.create(existingObj);

null can also be passed as an argument which means the new object would not have any prototype.

const newObj = Object.create(null)

Return value

The return value of this method is an empty object. Yes, the object is literally empty, but it contains hidden properties which contains the contents of the prototype.

Example

const obj = {
    name: "Javascript",
    print: function() {
        return 'Prototype'
    }
}
const newObj = Object.create(obj);
console.log(newObj)
console.log(newObj.name)
// Expected output
// {}
// Javascript

As you can see, when newObj is logged, an empty object is gotten, but newObj.name outputs the name property of it's object prototype. Let's check the properties of newObj

console.log(newObj);

When you check the output in the console, you'll see an empty object, with the same __proto__ property which contains all the properties and methods of obj. You'll also find another __proto__. As you may have thought, the second __proto__ references the global Object prototype. Remember I said that all objects are creaed from the Object prototype. So even if obj was used as prototype for another object, it also has it's own existing prototype.

Wrap up

There's a lot in how prototypes work but this article was created to explain the Object.create method.

One benefit of this prototype feature is how Javascript implements classes. Check out this article for more information - How Javascript Implements Blass-based Object Oriented Programming

For more understanding of Object.create, check out the MDN documentation

Thanks for reading 💛

If you have any questions or contributions regarding this article, kindly reach Dillion Megida (@iamdillion) or visit us on twitter - @thewebfor5

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