


Explanation of the difference between js regular expression exec and match_javascript skills
JS regular expressions were rarely used in the past when using JS. Even if they were used, they were used to judge things like email names. There are many codes on the Internet and little research. They can be used immediately.
Recently, I have encountered some problems that require the use of regular expressions. Let’s study them by the way
Regular expression objects are defined in two ways:
1. The first definition:
new RegExp(pattern, attributes); such as var reg = new RegExp("abc","g")
Pattern represents the expression content, as shown above, it matches abc
Attributes: g, global matching, i is not case-sensitive, m performs multi-line matching, the most commonly used ones are g and i
2. The second definition:/pattern/attributes.
For example: var reg = /abc/g;
Some rules of regular expression are not explained here. Only the difference between exec and match is recorded:
1. exec is a regular expression method, not a string method. Its parameter is a string, as shown below:
As defined above
var reg = new RegExp("abc");
var str = "3abc4, 5abc6";
reg.exec(str);
2. Match is a method for strings to execute matching regular expression rules. Its parameters are regular expressions, such as
var reg = new RegExp("abc") ;
var str = "3abc4,5abc6";
str.match(reg);
3. exec and match return arrays;
If the regular expression executed by exec has no subexpression (the content within parentheses, such as (s*) in /abc(s*)/), if there is a match, the first matching string will be returned Content, the array at this time has only one element, if there is no match, null is returned;
var reg = new RegExp("abc") ;
var str = "3abc4,5abc6";
alert(reg.exec(str));
alert(str.match(reg) );
Execute the above code, you will find that the contents of both are the same: abc,
4. If you define the regular expression object as global matching, such as:
var reg = new RegExp("abc","g") ;
var str = "3abc4,5abc6";
alert(reg.exec(str));
alert(str. match(reg));
is abc and abc, abc; because match executes a global matching query; and exec will only find a matching one and return it if there is no subexpression.
5. When the expression contains subexpressions:
var reg = new RegExp("a(bc)") ;
var str = "3abc4,5abc6";
alert(reg.exec(str));
alert(str.match (reg));
You will find that the results of both executions are: abc, bc;
6. When the if regular expression object is defined as a global match
var reg = new RegExp("a(bc)","g") ;
var str = "3abc4,5abc6";
alert(reg.exec(str));
alert (str.match(reg));
The results returned by the two are abc,bc and abc,abc,
is summarized as:
1. When the regular expression has no subexpression and is defined as a non-global match, the execution results of exec and match are the same, and both return the first matched string content;
2. When the regular expression has no subexpression and is defined as a global match, exec and match are executed, and if there are multiple matching contents, match returns an array of multiple elements;
3. When the regular expression has sub-representations and is defined as a non-global match, the execution results of exec and match are the same as in the 5th case above;
4. When the regular expression has sub-expressions and is defined as a global match, the execution results of exec and match are different. At this time, match will ignore the sub-expression and only search for the full matching regular expression and return all contents. As in case 6 above;
In other words, exec has nothing to do with whether the global is defined, while match is related to the global. When defined as non-global, the execution results of the two are the same

JavaScript's applications in the real world include server-side programming, mobile application development and Internet of Things control: 1. Server-side programming is realized through Node.js, suitable for high concurrent request processing. 2. Mobile application development is carried out through ReactNative and supports cross-platform deployment. 3. Used for IoT device control through Johnny-Five library, suitable for hardware interaction.

I built a functional multi-tenant SaaS application (an EdTech app) with your everyday tech tool and you can do the same. First, what’s a multi-tenant SaaS application? Multi-tenant SaaS applications let you serve multiple customers from a sing

This article demonstrates frontend integration with a backend secured by Permit, building a functional EdTech SaaS application using Next.js. The frontend fetches user permissions to control UI visibility and ensures API requests adhere to role-base

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 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.

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.

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.

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.


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

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

Atom editor mac version download
The most popular open source editor

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

WebStorm Mac version
Useful JavaScript development tools

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.