Web Front-end
JS Tutorial
Implementing function overloading and parameter default values in JavaScript
Implementing function overloading and parameter default values in JavaScript
Parameter default value means that if an actual parameter is omitted when calling a function, the function will automatically assign a default value to the parameter, greatly improving the convenience and flexibility of function calling.
For example, take the string interception function substr(string,start,length) in PHP. When length is not specified, the function will intercept the start position in the string to the end of the string by default. If length is specified, then Intercept the string with length starting from the start position, so if you call substr('http://www.hualai.net.cn',11,6), hualai will be returned; if you omit the last One parameter, substr('http://www.hualai.net.cn',11), returns hualai.net.cn.
For example, in the jQuery framework, the $(selector).html() method is to obtain the HTML code within the element, while $(selector).html(content) is to set the HTML within the element. We know that in C language, we can set default values for function parameters in the following form:
void foo(int a, int b = 1, bool c = false);
In Java, you can set the default value of function parameters through function overloading:
public void foo(int a){
foo(a, 1);
}
public void foo(int a, int b){
foo(a, b, false);
}
public void foo(int a, int b, bool c){
//Function content
}
And in JavaScript , how to set the default value of function parameters like jQuery? There is no method in JavaScript to assign values directly after the parameters when defining a function in C language, nor is there any function overloading like in Java. However, we can achieve this through an arguments read-only variable array in the JavaScript method, as follows:
function foo(){
var a = arguments[0] ? arguments[0] : 1;
var b = arguments[1] ? arguments[1] : false;
//Function content
}
The above is by judging whether the parameter exists. If it does not exist, the default value is attached to the variable. We can overload by judging the type of the parameter:
function foo(){
if(typeof arguments[ 0] == 'string')
alert('The parameter type is a string');
else if(typeof arguments[0] == 'number')
alert('The parameter type is a numeric value');
}
or
function foo(){
if(arguments[0].constructor == String)
alert('The parameter type is a string');
else if(arguments[0].constructor == Number )
alert('The parameter type is a numeric value');
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
How to implement an online speech recognition system using WebSocket and JavaScript
Dec 17, 2023 pm 02:54 PM
How to use WebSocket and JavaScript to implement an online speech recognition system Introduction: With the continuous development of technology, speech recognition technology has become an important part of the field of artificial intelligence. The online speech recognition system based on WebSocket and JavaScript has the characteristics of low latency, real-time and cross-platform, and has become a widely used solution. This article will introduce how to use WebSocket and JavaScript to implement an online speech recognition system.
WebSocket and JavaScript: key technologies for implementing real-time monitoring systems
Dec 17, 2023 pm 05:30 PM
WebSocket and JavaScript: Key technologies for realizing real-time monitoring systems Introduction: With the rapid development of Internet technology, real-time monitoring systems have been widely used in various fields. One of the key technologies to achieve real-time monitoring is the combination of WebSocket and JavaScript. This article will introduce the application of WebSocket and JavaScript in real-time monitoring systems, give code examples, and explain their implementation principles in detail. 1. WebSocket technology
How to use JavaScript and WebSocket to implement a real-time online ordering system
Dec 17, 2023 pm 12:09 PM
Introduction to how to use JavaScript and WebSocket to implement a real-time online ordering system: With the popularity of the Internet and the advancement of technology, more and more restaurants have begun to provide online ordering services. In order to implement a real-time online ordering system, we can use JavaScript and WebSocket technology. WebSocket is a full-duplex communication protocol based on the TCP protocol, which can realize real-time two-way communication between the client and the server. In the real-time online ordering system, when the user selects dishes and places an order
How to implement an online reservation system using WebSocket and JavaScript
Dec 17, 2023 am 09:39 AM
How to use WebSocket and JavaScript to implement an online reservation system. In today's digital era, more and more businesses and services need to provide online reservation functions. It is crucial to implement an efficient and real-time online reservation system. This article will introduce how to use WebSocket and JavaScript to implement an online reservation system, and provide specific code examples. 1. What is WebSocket? WebSocket is a full-duplex method on a single TCP connection.
JavaScript and WebSocket: Building an efficient real-time weather forecasting system
Dec 17, 2023 pm 05:13 PM
JavaScript and WebSocket: Building an efficient real-time weather forecast system Introduction: Today, the accuracy of weather forecasts is of great significance to daily life and decision-making. As technology develops, we can provide more accurate and reliable weather forecasts by obtaining weather data in real time. In this article, we will learn how to use JavaScript and WebSocket technology to build an efficient real-time weather forecast system. This article will demonstrate the implementation process through specific code examples. We
Simple JavaScript Tutorial: How to Get HTTP Status Code
Jan 05, 2024 pm 06:08 PM
JavaScript tutorial: How to get HTTP status code, specific code examples are required. Preface: In web development, data interaction with the server is often involved. When communicating with the server, we often need to obtain the returned HTTP status code to determine whether the operation is successful, and perform corresponding processing based on different status codes. This article will teach you how to use JavaScript to obtain HTTP status codes and provide some practical code examples. Using XMLHttpRequest
How to use insertBefore in javascript
Nov 24, 2023 am 11:56 AM
Usage: In JavaScript, the insertBefore() method is used to insert a new node in the DOM tree. This method requires two parameters: the new node to be inserted and the reference node (that is, the node where the new node will be inserted).
JavaScript and WebSocket: Building an efficient real-time image processing system
Dec 17, 2023 am 08:41 AM
JavaScript is a programming language widely used in web development, while WebSocket is a network protocol used for real-time communication. Combining the powerful functions of the two, we can create an efficient real-time image processing system. This article will introduce how to implement this system using JavaScript and WebSocket, and provide specific code examples. First, we need to clarify the requirements and goals of the real-time image processing system. Suppose we have a camera device that can collect real-time image data
