![]() Alas, with subclassing, you have no choice and have to set the constructor property yourself. > Object.getOwnPropertyNames(f.prototype)īest practice: Avoid replacing the complete prototype value of a constructor with your own object and only add new properties to it. JavaScript even sets up that property for you: > Object.getOwnPropertyNames(Object.getPrototypeOf(f)) It turns out that an instance does not own the constructor property, but inherits it from its prototype: Where does the constructor property come from? Is determined by whether C.prototype is in the prototype chain of obj. Note that the instanceof operator does not use the constructor property. It can be used to similar effect in methods: Sub.prototype = Object.create(Sub.superclass) Īssigning the super-prototype to Sub.superclass avoids the hardcoded use of the superclass name in the sub-constructor. Invoking a super-constructor: You need the constructor property at (*), below.This is mainly useful if you have several subclasses and want to clone an instance. Create a new instance: Given an object, you can create a new instance that has the same class.For example, the following two instances of String have the same class: Thus, getting the constructor of an object gives you its class. Get the class of an object: Remember that constructor functions can be considered classes in JavaScript.The constructor property serves three purposes: If you examine the property, you’ll find out that it points to – surprise – the constructor of an object. Sets the prototype of this object to the constructor functions prototype property. The new keyword has to be placed before the constructor function call and will do the following things: Creates a new object. This post explains what that property is all about. Summary: The new keyword is used in JavaScript to create a object from a constructor function. All objects produced by built-in constructor functions in JavaScript have a property called constructor.
0 Comments
Leave a Reply. |