


The difference between call() and apply() in JavaScript_javascript tips
If you have never been exposed to dynamic languages, it will be a magical and weird feeling to understand JavaScript with the way of thinking of compiled languages, because things that are consciously impossible often happen, and even feel unreasonable. If you are learning When you encounter this feeling in the process of JavaScript, a free and ever-changing language, then from now on, please put down your "prejudice", because this is definitely a new continent for you, let JavaScript
Okay, let’s get back to the subject. First, understand the dynamic change runtime context feature of JavaScrtipt. This feature is mainly reflected in the use of the apply and call methods.
1. Definition of method
call method:
Syntax: call(thisObj, Object)Definition: Call a method of an object to replace the current object with another object.
The call method can be used to call a method on behalf of another object. The call method changes the object context of a function from the initial context to the new object specified by thisObj.
If no thisObj parameter is provided, the Global object is used as thisObj.
apply method:
Syntax: apply(thisObj, [argArray])Definition: Apply a method of an object to replace the current object with another object.
Description:
If argArray is not a valid array or is not an arguments object, a TypeError will be caused.
If neither argArray nor thisObj is provided, the Global object will be used as thisObj and no parameters can be passed.
Note: The call and apply methods are exactly the same, except that apply uses an array to pass parameters.
function Animal(name) { this.name = name; this.showName = function() { console.log(this.name); }; } function Cat(name) { Animal.call(this, name); } Cat.prototype = new Animal(); function Dog(name) { Animal.apply(this, name); } Dog.prototype = new Animal(); var cat = new Cat("Black Cat"); //call必须是object var dog = new Dog(["Black Dog"]); //apply必须是array cat.showName(); dog.showName(); console.log(cat instanceof Animal); console.log(dog instanceof Animal);
function Animal(name) { this.name = name; this.showName = function() { alert(this.name); }; }; function Cat(name) { this.superClass = Animal; this.superClass(name); delete superClass; } var cat = new Cat("Black Cat"); cat.showName();
Summary:
Their respective definitions:
apply: Apply a method of an object and replace the current object with another object.call: Call a method of an object to replace the current object with another object.
What they have in common:
Both "can be used to call a method instead of another object, changing the object context of a function from the initial context to the new object specified by thisObj." - Excerpted from JScript5.5.chm
Their differences:
apply: There can only be two parameters at most - the new this object and an array argArray. If multiple parameters are passed to this method, all parameters will be written into this array. Of course, even if there is only one parameter, it will be written into the array. If argArray is not a valid array or is not an arguments object, a TypeError will be caused. If neither argArray nor thisObj are provided, the Global object will be used as thisObj and no parameters can be passed.call: It is a direct parameter list, mainly used when various methods of js objects call each other to keep the current this instance pointer consistent, or to change this pointer under special circumstances. If no thisObj parameter is provided, the Global object is used as thisObj.
To put it more simply, the functions of apply and call are the same, but the form of the parameter list passed in is different: for example, the corresponding apply writing method of func.call(func1,var1,var2,var3) is: func.apply(func1,[var1 ,var2,var3])

Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics



Frequently Asked Questions and Solutions for Front-end Thermal Paper Ticket Printing In Front-end Development, Ticket Printing is a common requirement. However, many developers are implementing...

There is no absolute salary for Python and JavaScript developers, depending on skills and industry needs. 1. Python may be paid more in data science and machine learning. 2. JavaScript has great demand in front-end and full-stack development, and its salary is also considerable. 3. Influencing factors include experience, geographical location, company size and specific skills.

JavaScript is the cornerstone of modern web development, and its main functions include event-driven programming, dynamic content generation and asynchronous programming. 1) Event-driven programming allows web pages to change dynamically according to user operations. 2) Dynamic content generation allows page content to be adjusted according to conditions. 3) Asynchronous programming ensures that the user interface is not blocked. JavaScript is widely used in web interaction, single-page application and server-side development, greatly improving the flexibility of user experience and cross-platform development.

How to merge array elements with the same ID into one object in JavaScript? When processing data, we often encounter the need to have the same ID...

Discussion on the realization of parallax scrolling and element animation effects in this article will explore how to achieve similar to Shiseido official website (https://www.shiseido.co.jp/sb/wonderland/)...

In-depth discussion of the root causes of the difference in console.log output. This article will analyze the differences in the output results of console.log function in a piece of code and explain the reasons behind it. �...

Learning JavaScript is not difficult, but it is challenging. 1) Understand basic concepts such as variables, data types, functions, etc. 2) Master asynchronous programming and implement it through event loops. 3) Use DOM operations and Promise to handle asynchronous requests. 4) Avoid common mistakes and use debugging techniques. 5) Optimize performance and follow best practices.

Explore the implementation of panel drag and drop adjustment function similar to VSCode in the front-end. In front-end development, how to implement VSCode similar to VSCode...
