正则表达式元字符是包含特殊含义的字符。它们有一些特殊功能，可以控制匹配模式的方式。反斜杠后的元字符将失去其特殊含义。

字符类：单个字符和数字

字符类：空白字符

字符类：锚字符

字符类：重复字符

字符类：替代字符

字符类：记录字符

/*使用点元字符*/

var pattern = /g..gle/; //.匹配一个任意字符

var str = ‘google‘;

alert(pattern.test(str));

/*重复匹配*/

var pattern = /g.*gle/; //.匹配0个一个或多个

var str = ‘google‘; //*,?,+,{n,m}

alert(pattern.test(str));

/*使用字符类匹配*/

var pattern = /g[a-zA-Z_]*gle/; //[a-z]*表示任意个a-z中的字符

var str = ‘google‘;

alert(pattern.test(str));

var pattern = /g[^0-9]*gle/; //[^0-9]*表示任意个非0-9的字符

var str = ‘google‘;

alert(pattern.test(str));

var pattern = /[a-z][A-Z]+/; //[A-Z]+表示A-Z一次或多次

var str = ‘gOOGLE‘;

alert(pattern.test(str));

/*使用元符号匹配*/

var pattern = /g\w*gle/; //\w*匹配任意多个所有字母数字_

var str = ‘google‘;

alert(pattern.test(str));

var pattern = /google\d*/; //\d*匹配任意多个数字

var str = ‘google444‘;

alert(pattern.test(str));

var pattern = /\D{7,}/; //\D{7,}匹配至少7个非数字

var str = ‘google8‘;

alert(pattern.test(str));

/*使用锚元字符匹配*/

var pattern = /^google$/; //^从开头匹配，$从结尾开始匹配

var str = ‘google‘;

alert(pattern.test(str));

var pattern = /goo\sgle/; //\s可以匹配到空格

var str = ‘goo gle‘;

alert(pattern.test(str));

var pattern = /google\b/; //\b可以匹配是否到了边界

var str = ‘google‘;

alert(pattern.test(str));

/*使用或模式匹配*/

var pattern = /google|baidu|bing/; //匹配三种其中一种字符串

var str = ‘google‘;

alert(pattern.test(str));

/*使用分组模式匹配*/

var pattern = /(google){4,8}/; //匹配分组里的字符串4-8次

var str = ‘googlegoogle‘;

alert(pattern.test(str));

var pattern = /8(.*)8/; //获取8..8之间的任意字符

var str = ‘This is 8google8‘;

str.match(pattern);

alert(RegExp.$1); //得到第一个分组里的字符串内容

var pattern = /8(.*)8/;

var str = ‘This is 8google8‘;

var result = str.replace(pattern,‘<strong>$1</strong>‘); //得到替换的字符串输出

document.write(result);

var pattern = /(.*)\s(.*)/;

var str = ‘google baidu‘;

var result = str.replace(pattern, ‘$2 $1‘); //将两个分组的值替换输出

document.write(result);

/*关于贪婪和惰性*/

var pattern = /[a-z]+?/; //?号关闭了贪婪匹配，只替换了第一个

var str = ‘abcdefjhijklmnopqrstuvwxyz‘;

var result = str.replace(pattern, ‘xxx‘);

alert(result);

var pattern = /8(.+?)8/g; //禁止了贪婪，开启的全局

var str = ‘This is 8google8, That is 8google8, There is 8google8‘;

var result = str.replace(pattern,‘<strong>$1</strong>‘);

document.write(result);

var pattern = /8([^8]*)8/g; //另一种禁止贪婪

var str = ‘This is 8google8, That is 8google8, There is 8google8‘;

var result = str.replace(pattern,‘<strong>$1</strong>‘);

document.write(result);

/*使用exec返回数组*/

var pattern = /^[a-z]+\s[0-9]{4}$/i;

var str = ‘google 2012‘;

alert(pattern.exec(str)); //返回整个字符串

var pattern = /^[a-z]+/i; //只匹配字母

var str = ‘google 2012‘;

alert(pattern.exec(str)); //返回google

var pattern = /^([a-z]+)\s([0-9]{4})$/i; //使用分组

var str = ‘google 2012‘;

alert(pattern.exec(str)[0]); //google 2012

alert(pattern.exec(str)[1]); //google

alert(pattern.exec(str)[2]); //2012

/*捕获性分组和非捕获性分组*/

var pattern = /(\d+)([a-z])/; //捕获性分组

var str = ‘123abc‘;

alert(pattern.exec(str));

var pattern = /(\d+)(?:[a-z])/; //非捕获性分组

var str = ‘123abc‘;

alert(pattern.exec(str));

/*使用分组嵌套*/

var pattern = /(A?(B?(C?)))/; //从外往内获取

var str = ‘ABC‘;

alert(pattern.exec(str));

/*使用前瞻捕获*/

var pattern = /(goo(?=gle))/; //goo后面必须跟着gle才能捕获

var str = ‘google‘;

alert(pattern.exec(str));

/*使用特殊字符匹配*/

var pattern = /\.\[\/b\]/; //特殊字符，用\符号转义即可

var str = ‘.[/b]‘;

alert(pattern.test(str));

/*使用换行模式*/

var pattern = /^\d+/mg; //启用了换行模式

var str = ‘1.baidu\n2.google\n3.bing‘;

var result = str.replace(pattern, ‘#‘);

alert(result);

三．常用的正则

1.检查邮政编码

var pattern = /[1-9][0-9]{5}/; //共6位数字，第一位不能为0

var str = ‘224000‘;

alert(pattern.test(str));

2.检查文件压缩包

var pattern = /[\w]+\.zip|rar|gz/; //\w表示所有数字和字母加下划线

var str = ‘123.zip‘; //\.表示匹配.，后面是一个选择

alert(pattern.test(str));

3.删除多余空格

var pattern = /\s/g; //g必须全局，才能全部匹配

var str = ‘111 222 333‘;

var result = str.replace(pattern,‘‘); //把空格匹配成无空格

alert(result);

4.删除首尾空格

var pattern = /^\s+/; //强制首

var str = ‘          goo  gle            ‘;

var result = str.replace(pattern, ‘‘);

pattern = /\s+$/; //强制尾

result = result.replace(pattern, ‘‘);

alert(‘|‘ + result + ‘|‘);

var pattern = /^\s*(.+?)\s*$/; //使用了非贪婪捕获

var str = ‘            google          ‘;

alert(‘|‘ + pattern.exec(str)[1] + ‘|‘);

var pattern = /^\s*(.+?)\s*$/;

var str = ‘            google          ‘;

alert(‘|‘ + str.replace(pattern, ‘$1‘) + ‘|‘); //使用了分组获取

5.简单的电子邮件验证

var pattern = /^([a-zA-Z0-9_\.\-]+)@([a-zA-Z0-9_\.\-]+)\.([a-zA-Z]{2,4})$/;

var str = ‘yc60.com@gmail.com‘;

alert(pattern.test(str));

var pattern = /^([\w\.\-]+)@([\w\.\-]+)\.([\w]{2,4})$/;

var str = ‘yc60.com@gmail.com‘;

alert(pattern.test(str));

正则表达式