Tutorials References Menu

JS Tutorial

JS HOME JS Introduction JS Where To JS Output JS Statements JS Syntax JS Comments JS Variables JS Let JS Const JS Operators JS Arithmetic JS Assignment JS Data Types JS Functions JS Objects JS Events JS Strings JS String Methods JS String Search JS Numbers JS Number Methods JS Arrays JS Array Methods JS Array Sort JS Array Iteration JS Array Const JS Dates JS Date Formats JS Date Get Methods JS Date Set Methods JS Math JS Random JS Booleans JS Comparisons JS Conditions JS Switch JS Loop For JS Loop For In JS Loop For Of JS Loop While JS Break JS Typeof JS Type Conversion JS Bitwise JS RegExp JS Errors JS Scope JS Hoisting JS Strict Mode JS this Keyword JS Arrow Function JS Classes JS JSON JS Debugging JS Style Guide JS Best Practices JS Mistakes JS Performance JS Reserved Words

JS Objects

Object Definitions Object Properties Object Methods Object Display Object Accessors Object Constructors Object Prototypes Object Reference Object Map() Object Set()

JS Functions

Function Definitions Function Parameters Function Invocation Function Call Function Apply Function Closures

JS Classes

Class Intro Class Inheritance Class Static

JS Async

JS Callbacks JS Asynchronous JS Promises JS Async/Await

JS Versions

JS Versions JS 2009 (ES5) JS 2015 (ES6) JS 2016 JS 2017 JS 2018 JS IE / Edge JS History

JS HTML DOM

DOM Intro DOM Methods DOM Document DOM Elements DOM HTML DOM Forms DOM CSS DOM Animations DOM Events DOM Event Listener DOM Navigation DOM Nodes DOM Collections DOM Node Lists

JS Browser BOM

JS Window JS Screen JS Location JS History JS Navigator JS Popup Alert JS Timing JS Cookies

JS Web APIs

Web API Intro Web Forms API Web History API Web Storage API Web Worker API Web Fetch API Web Geolocation API

JS AJAX

AJAX Intro AJAX XMLHttp AJAX Request AJAX Response AJAX XML File AJAX PHP AJAX ASP AJAX Database AJAX Applications AJAX Examples

JS JSON

JSON Intro JSON Syntax JSON vs XML JSON Data Types JSON Parse JSON Stringify JSON Objects JSON Arrays JSON Server JSON PHP JSON HTML JSON JSONP

JS vs jQuery

jQuery Selectors jQuery HTML jQuery CSS jQuery DOM

JS Examples

JS Examples JS HTML DOM JS HTML Input JS HTML Objects JS HTML Events JS Browser JS Editor

JS References

JavaScript Objects HTML DOM Objects


JavaScript Function Apply


Method Reuse

With the apply() method, you can write a method that can be used on different objects.


The JavaScript apply() Method

The apply() method is similar to the call() method (previous chapter).

In this example the fullName method of person is applied on person1:

Example

const person = {
  fullName: function() {
    return this.firstName + " " + this.lastName;
  }
}

const person1 = {
  firstName: "Mary",
  lastName: "Doe"
}

// This will return "Mary Doe":
person.fullName.apply(person1);

Try it Yourself »


The Difference Between call() and apply()

The difference is:

The call() method takes arguments separately.

The apply() method takes arguments as an array.

The apply() method is very handy if you want to use an array instead of an argument list.


The apply() Method with Arguments

The apply() method accepts arguments in an array:

Example

const person = {
  fullName: function(city, country) {
    return this.firstName + " " + this.lastName + "," + city + "," + country;
  }
}

const person1 = {
  firstName:"John",
  lastName: "Doe"
}

person.fullName.apply(person1, ["Oslo", "Norway"]);

Try it Yourself »

Compared with the call() method:

Example

const person = {
  fullName: function(city, country) {
    return this.firstName + " " + this.lastName + "," + city + "," + country;
  }
}

const person1 = {
  firstName:"John",
  lastName: "Doe"
}

person.fullName.call(person1, "Oslo", "Norway");

Try it Yourself »



Simulate a Max Method on Arrays

You can find the largest number (in a list of numbers) using the Math.max() method:

Example

Math.max(1,2,3);  // Will return 3

Try it Yourself »

Since JavaScript arrays do not have a max() method, you can apply the Math.max() method instead.

Example

Math.max.apply(null, [1,2,3]); // Will also return 3

Try it Yourself »

The first argument (null) does not matter. It is not used in this example.

These examples will give the same result:

Example

Math.max.apply(Math, [1,2,3]); // Will also return 3

Try it Yourself »

Example

Math.max.apply(" ", [1,2,3]); // Will also return 3

Try it Yourself »

Example

Math.max.apply(0, [1,2,3]); // Will also return 3

Try it Yourself »


JavaScript Strict Mode

In JavaScript strict mode, if the first argument of the apply() method is not an object, it becomes the owner (object) of the invoked function. In "non-strict" mode, it becomes the global object.