search
HomeWeb Front-endJS TutorialGlobal matching pattern analysis of regular expressions in Javascript_javascript skills

Copy code The code is as follows:

var str = "123#abc";
var re = /abc/ig;
console.log(re.test(str)); //Output true
console.log(re.test(str)); //Output false
console.log( re.test(str)); //Output true
console.log(re.test(str)); //Output false

If used when creating a regular expression object When the "g" identifier or its global attribute value is set to true, the newly created regular expression object will use the pattern to globally match the string to be matched. In global matching mode, multiple matches can be performed on the specified string to be found. Each match uses the value of the lastIndex attribute of the current regular object as the starting position to start searching in the target string. The initial value of the lastIndex attribute is 0. After a matching item is found, the value of lastIndex is reset to the position index of the next character of the matching content in the string, which is used to identify the position where to start searching the next time a match is performed. If no matching item is found the value of lastIndex will be set to 0. When the global matching flag of the regular object is not set, the value of the lastIndex attribute is always 0, and each time a match is performed, only the first matching item in the string is found. You can use the following code to view the value of the corresponding lastIndex attribute that matches the execution.
Copy code The code is as follows:

var str = "123#abc";
var re = /abc/ig;
console.log(re.test(str)); //Output ture
console.log(re.lastIndex); //Output 7
console.log( re.test(str)); //Output false
console.log(re.lastIndex); //Output 0
console.log(re.test(str)); //Output true
console.log(re.lastIndex); //Output 7
console.log(re.test(str)); //Output false
console.log(re.lastIndex); //Output 0

About the RegExp.prototype.exec(str) method and the String.prototype.math(rgExp) method

The test method of the regular object returns a value of true or false, and only needs to detect the target This method is useful when checking whether a string matches a specified pattern, but does not need to obtain the matching content. When you need to obtain the matching result, you need to use the exec(str) method of the RegExp type or the match(rgExp) method of the String type.

The RegExp.prototype.exec(str) method returns NULL or an array. The 0th element of the array stores the matching content found in the string str. 1 to n elements are returned. is the content of the submatch specified using brackets "()" in the pattern.

The String.prototype.math(rgExp) method behaves similarly to RegExp.prototype.exec(str) when no global flag is used. When the global match flag is set, the array item elements 0 to n returned by the String.prototype.math(rgExp) method contain all matched items excluding submatches. At this time, you can use RegExp.$1..$9 to obtain 9 submatches.
Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
JavaScript: Exploring the Versatility of a Web LanguageJavaScript: Exploring the Versatility of a Web LanguageApr 11, 2025 am 12:01 AM

JavaScript is the core language of modern web development and is widely used for its diversity and flexibility. 1) Front-end development: build dynamic web pages and single-page applications through DOM operations and modern frameworks (such as React, Vue.js, Angular). 2) Server-side development: Node.js uses a non-blocking I/O model to handle high concurrency and real-time applications. 3) Mobile and desktop application development: cross-platform development is realized through ReactNative and Electron to improve development efficiency.

The Evolution of JavaScript: Current Trends and Future ProspectsThe Evolution of JavaScript: Current Trends and Future ProspectsApr 10, 2025 am 09:33 AM

The latest trends in JavaScript include the rise of TypeScript, the popularity of modern frameworks and libraries, and the application of WebAssembly. Future prospects cover more powerful type systems, the development of server-side JavaScript, the expansion of artificial intelligence and machine learning, and the potential of IoT and edge computing.

Demystifying JavaScript: What It Does and Why It MattersDemystifying JavaScript: What It Does and Why It MattersApr 09, 2025 am 12:07 AM

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.

Is Python or JavaScript better?Is Python or JavaScript better?Apr 06, 2025 am 12:14 AM

Python is more suitable for data science and machine learning, while JavaScript is more suitable for front-end and full-stack development. 1. Python is known for its concise syntax and rich library ecosystem, and is suitable for data analysis and web development. 2. JavaScript is the core of front-end development. Node.js supports server-side programming and is suitable for full-stack development.

How do I install JavaScript?How do I install JavaScript?Apr 05, 2025 am 12:16 AM

JavaScript does not require installation because it is already built into modern browsers. You just need a text editor and a browser to get started. 1) In the browser environment, run it by embedding the HTML file through tags. 2) In the Node.js environment, after downloading and installing Node.js, run the JavaScript file through the command line.

How to send notifications before a task starts in Quartz?How to send notifications before a task starts in Quartz?Apr 04, 2025 pm 09:24 PM

How to send task notifications in Quartz In advance When using the Quartz timer to schedule a task, the execution time of the task is set by the cron expression. Now...

In JavaScript, how to get parameters of a function on a prototype chain in a constructor?In JavaScript, how to get parameters of a function on a prototype chain in a constructor?Apr 04, 2025 pm 09:21 PM

How to obtain the parameters of functions on prototype chains in JavaScript In JavaScript programming, understanding and manipulating function parameters on prototype chains is a common and important task...

What is the reason for the failure of Vue.js dynamic style displacement in the WeChat mini program webview?What is the reason for the failure of Vue.js dynamic style displacement in the WeChat mini program webview?Apr 04, 2025 pm 09:18 PM

Analysis of the reason why the dynamic style displacement failure of using Vue.js in the WeChat applet web-view is using Vue.js...

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. How to Fix Audio if You Can't Hear Anyone
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
WWE 2K25: How To Unlock Everything In MyRise
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Safe Exam Browser

Safe Exam Browser

Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

PhpStorm Mac version

PhpStorm Mac version

The latest (2018.2.1) professional PHP integrated development tool