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
php怎么去除字符串中的所有大写字母php怎么去除字符串中的所有大写字母Sep 26, 2022 pm 07:59 PM

两种去除方法:1、利用preg_replace()执行正则表达式搜索所有大写字母并将其替换为空字符即可,语法“preg_replace('/[A-Z]/','',$str)”。2、利用preg_filter()执行正则表达式搜索所有大写字母并将其替换为空字符即可,语法“preg_filter('/[A-Z]/','',$str)”。

php怎么替换nbsp空格符php怎么替换nbsp空格符Apr 24, 2022 pm 02:55 PM

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\&nbsp\;||\xc2\xa0)/","其他字符",$str)”语句。

使用Go语言编写高性能的正则表达式匹配使用Go语言编写高性能的正则表达式匹配Jun 15, 2023 pm 10:56 PM

随着数据量的不断增大,正则表达式匹配成为了程序中常用的操作之一。而在Go语言中,由于其天然的并行ism,以及与底层系统的交互性和高效性,使得Go语言的正则表达式匹配极具优势。那么如何使用Go语言编写高性能的正则表达式匹配呢?一、了解正则表达式在使用正则表达式前,我们首先需要了解正则表达式,了解其基本语法规则以及常用的匹配字符,使我们能够在编写正则表达式时更加

php怎么利用正则排除字符串中的字符php怎么利用正则排除字符串中的字符Dec 15, 2022 pm 03:30 PM

两种方法:1、用preg_replace(),可执行正则表达式的搜索和替换,只需将字符串中匹配的字符替换为空字符即可,语法“preg_replace(正则, "", $str)”。2、用preg_match_all(),可搜索字符串中所有和正则表达式匹配的结果,会将每次的匹配结果放在一个数组$array中,语法“preg_match_all(正则,$str,$array);”。

php怎么只获取中文字符php怎么只获取中文字符Apr 28, 2022 pm 08:15 PM

php中可用preg_match_all()配合正则表达式过滤字符串,只获取中文字符;语法“preg_match_all("/[\x{4e00}-\x{9fff}]+/u","$str",$arr);”,会将匹配字符存入“$arr”数组中。

javascript怎么正则替换非汉字的字符javascript怎么正则替换非汉字的字符Oct 13, 2022 pm 05:37 PM

在javascript中,可以使用replace()函数配合正则表达式“/[u4e00-u9fa5|,]+/ig”来查找字符串中的所有非汉字字符,并将其替换为其他指定值,语法“字符串对象.replace(/[u4e00-u9fa5|,]+/ig,'指定替换值')”。

Java语言正则表达式的使用方法Java语言正则表达式的使用方法Jun 10, 2023 am 08:13 AM

Java语言正则表达式的使用方法正则表达式是一种强大的文本处理工具,可以用来匹配和验证文本。在Java语言中,也可以使用正则表达式来实现字符串的匹配和处理。本文将介绍Java语言正则表达式的使用方法,涵盖正则表达式的基础知识,常用的正则表达式语法,以及在Java程序中使用正则表达式的方法。一、基础知识正则表达式是什么?正则表达式是一种文本模式,用来描述一组字

PHP开发:如何编写高效的正则表达式PHP开发:如何编写高效的正则表达式Jun 15, 2023 pm 09:04 PM

在PHP开发中,正则表达式是非常重要的工具,用于匹配、查找和替换文本中的特定字符串。然而,编写高效的正则表达式并不是一件易事,需要开发者具备一定的技巧和经验。下面是一些可以帮助您编写高效正则表达式的技巧:1.尽可能使用非贪婪匹配默认情况下,正则表达式是贪婪的,即它们将尽可能匹配更多的文本。在某些情况下,可能需要使用非贪婪匹配来避免这种情况。非贪婪匹配使用"

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)
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
2 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

Hot Tools

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

SublimeText3 Linux new version

SublimeText3 Linux new version

SublimeText3 Linux latest version

PhpStorm Mac version

PhpStorm Mac version

The latest (2018.2.1) professional PHP integrated development tool