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HomeWeb Front-endJS TutorialIntroduction to the use of JavaScript RegExp objects

Introduction to the use of JavaScript RegExp objects

May 07, 2018 am 10:00 AM
javascriptjsregexp

JavaScript RegExp 正则表达在验证表单等情况下运用频繁,所以本文详细的讲解正则的使用方法。

什么是 RegExp?

正则表达式描述了字符的模式对象。

当您检索某个文本时,可以使用一种模式来描述要检索的内容。RegExp 就是这种模式。

简单的模式可以是一个单独的字符。

更复杂的模式包括了更多的字符,并可用于解析、格式检查、替换等等。

您可以规定字符串中的检索位置,以及要检索的字符类型,等等。

语法

var patt=new RegExp(pattern,modifiers);

或更简单的方法

var patt=/pattern/modifiers;

模式描述了一个表达式模型。

修饰符(modifiers)描述了检索是否是全局,区分大小写等。

注意:当使用构造函数创造正则对象时,需要常规的字符转义规则(在前面加反斜杠 \)。比如,以下是等价的:

var re = new RegExp("\\w+");var re = /\w+/;

RegExp 修饰符

修饰符用于执行不区分大小写和全文的搜索。

i - 修饰符是用来执行不区分大小写的匹配。

g - 修饰符是用于执行全文的搜索(而不是在找到第一个就停止查找,而是找到所有的匹配)。

实例 1

在字符串中不区分大小写找"runoob"

var str = "Visit RUnoob";var patt1 = /runoob/i;

以下标记的文本是获得的匹配的表达式:

Visit RUnoob

实例 2

全文查找 "is"

var str="Is this all there is?";var patt1=/is/g;

以下标记的文本是获得的匹配的表达式:

Is this all there is?

实例 3

全文查找和不区分大小写搜索 "is"

var str="Is this all there is?";var patt1=/is/gi;

以下 标记的文本是获得的匹配的表达式:

Is this all there is?

test()

test()方法搜索字符串指定的值,根据结果并返回真或假。

下面的示例是从字符串中搜索字符 "e" :

实例

var patt1=new RegExp("e");document.write(patt1.test("The best things in life are free"));

由于该字符串中存在字母 "e",以上代码的输出将是:

true

当使用构造函数创造正则对象时,需要常规的字符转义规则(在前面加反斜杠 \)

实例

var re = new RegExp("\\w+");
exec()

exec() 方法检索字符串中的指定值。返回值是被找到的值。如果没有发现匹配,则返回 null。

下面的示例是从字符串中搜索字符 "e" :

实例 1

var patt1=new RegExp("e");document.write(patt1.exec("The best things in life are free"));

由于该字符串中存在字母 "e",以上代码的输出将是:

e

正则表达的使用较为广泛,本篇详细的讲解了正则的相关用法,想要观看更多的相关知识请关注php中文网。

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