JS array learning: traverse the array and double all element values
In the previous article, we learned about two methods of iterating arrays. If you are interested, you can click on the link to read → "JS array learning iterating arrays to calculate the sum of elements and concatenate the values into strings 》. This time we continue to learn JavaScript arrays and see how to traverse the array and process each element in the array (for example, all values are doubled). Friends in need can learn about it~
Traversing arrays , the first method that comes to mind is to use for loop, with which we can easily double all element values (that is, multiply by 2)
var a = [5,10,20];
for(var i=0;i<a.length;i++){
a[i]=2*a[i];
}
console.log(a);Output result:
#You can also use the for in statement to traverse the array. In the for/in loop structure, the variable i represents the subscript of the array, and a[i] is the element value that can read the specified subscript.
var a = [10,20,30];
for(var i in a){
a[i]=2*a[i];
}
console.log(a);Output result:
#You can also use the forEach() method mentioned in the previous article to traverse the array, This method can be called for each element of the array, passing the element to the callback function.
var a = [20,30,40];
function f(value) {
console.log(value*2);
}
a.forEach(f);Output result:
You can also use the map() method to traverse the array, the map() method can Calls the specified callback function on each element of the array and returns an array containing the results.
array.map(function callbackfn (value, index, array), thisArg);
function callbackfn (value, index, array): A callback function that accepts up to three parameters:
value: array element value.
index: Numeric index of the array element.
array: Array object containing the element.
Let’s learn more about it through code examples:
Example 1: Double the value of all elements (that is, multiply by 2)
var a = [30,40,50];
function f(value) {
return value*2;
}
var a1=a.map(f);
console.log(a1);Output result:
Example 2: Using JavaScript built-in methods as callback functions
var a = [9, 16]; var a1 = a.map(Math.sqrt); console.log(a1); //3,4
Okay, that’s all, you can read it if you need it ：javascript video tutorial
The above is the detailed content of JS array learning: traverse the array and double all element values. For more information, please follow other related articles on the PHP Chinese website!
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
