JavaScript Basics: Object.create

In an earlier post (Object Creation and Manipulation Functions in JavaScript), I listed some functions that are available on the Object constructor. Here is the list once again:

    create
    assign
    defineProperty
    defineProperties
    getPrototypeOf
    setPrototypeOf
    getOwnPropertyDescriptor
    getOwnPropertyDescriptors
    getOwnPropertyNames
    getOwnPropertySymbols
    is
    seal
    freeze
    preventExtensions
    isExtensible
    isSealed
    isFrozen
    keys
    entries
    values

And also these methods are on Object.prototype:

    hasOwnProperty
    isPrototypeOf
    propertyIsEnumerable

These functions are used for object creation and manipulation. In the current post, I am going to talk about the first one of these functions, Object.create.

Every constructor function in JavaScript has an associated prototype that is used as the prototype for the instances created by that constructor. In fact, the inheritance pattern in JavaScript is based on prototypes, so you can just create an object based on a prototype, without the need to define a constructor function. That's when Object.create becomes useful.

So Object.create creates an object based on a prototype. The prototype is specified as the first argument to this function. You can also specify a second argument that is a map of property names and property descriptors.

Here are some examples:

    let prototype = {
        name: "Ali",
        greet() {
            console.log("Hi. My name is " + this.name);
        },
    };
    
    let person1 = Object.create(prototype);
    
    let person2 = Object.create(prototype, {
        age: {
            value: 19,
            writable: true,
            enumerable: true,
            configurable: true,
        },
    });

As you see in the example, the second argument follows the same pattern used in Object.defineProperties.

Related Posts

• Object Creation and Manipulation Functions in JavaScript
• Property Descriptors in JavaScript
• Getting and Setting Property Descriptors in JavaScript (Part 1)
• Getting and Setting Property Descriptors in JavaScript (Part 2)
• Getting and Setting Property Descriptors in JavaScript (Part 3)
• Default Values of Property Descriptors in JavaScript