JavaScript - interesting trick, it is possible to create both class and function in one definition
In this article, we're going to have a look at how to create class that allows user to create object with or without new operator in JavaScript.
Problem overview:
xxxxxxxxxxfunction MyClass() { }var object1 = MyClass();var object2 = new MyClass(); // <----- how to make new operator optional?Simple problem solutions are presented below:
In this case recept how to make new object for same class definition with and without new keyword with strict mode is described.
Note: these approach work for web broser and NodeJS JavaScript with strict mode.
When this is not defined new object is cteated and assigned to self variable - it means ClassFunction was called as function.
xxxxxxxxxx'use strict'; // optional for NodeJSvar ClassFunction = function() { var self = this || { }; self.printText = function(text) { console.log(text); }; return self;};var object1 = ClassFunction();var object2 = new ClassFunction();object1.printText('This text comes from function result object!');object2.printText('This text comes from class instance object!');Below example shows how to detect if new keyword were used to create ClassFunction.
xxxxxxxxxx'use strict';var ClassFunction = function() { var self = this; if (self instanceof ClassFunction) { self.printText = function(text) { console.log(text); }; } else { return new ClassFunction(); }};var object1 = ClassFunction();var object2 = new ClassFunction();object1.printText('This text comes from function result object!');object2.printText('This text comes from class instance object!');
In this case recept how to make new object for same class definition with and without new keyword without strict mode is described.
Note: this approach requires to adjust source code for web browser or node js - look on comment - to solve this problem check example 2.
xxxxxxxxxxvar ClassFunction = function() { var self = (this == window || this == null ? {} : this); // for web browser// var self = (this == global || this == null ? {} : this); // for nodejs self.printText = function(text) { console.log(text); }; return self;};var object1 = ClassFunction();var object2 = new ClassFunction();object1.printText('This text comes from function result object!');object2.printText('This text comes from class instance object!');This universal approach is useful to write code for web browser and node js both.
xxxxxxxxxxfunction getRoot() { if (typeof window != 'undefined') { return window; } if (typeof global != 'undefined') { return global; } throw new Error('Unsupported platform!');}var root = getRoot();root.createScope = function(self) { return (self == root ? { } : self);};// Example:var ClassFunction = function() { var self = createScope(this); self.printText = function(text) { console.log(text); }; return self;}var object1 = ClassFunction();var object2 = new ClassFunction();object1.printText('This text comes from function result object!');object2.printText('This text comes from class instance object!');