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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