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Home > Web Front-end > JS Tutorial > How to match Abba's reverse lookahead with regular expressions

How to match Abba's reverse lookahead with regular expressions

php中世界最好的语言
Release： 2018-03-30 14:07:01
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这次给大家带来正则怎么匹配Abba逆向前瞻，正则匹配Abba逆向前瞻的注意事项有哪些，下面就是实战案例，一起来看一下。

核心代码：

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<script>

var s1 = 'acritan';

var s2 = 'bassarisk';

var s3 = 'commotive';

//找出不包含 "abba" 模式的单词

var r = /^(?!.*?(.)(.)\2\1)/i;

alert(r.test(s1)); // true

alert(r.test(s2)); // false

alert(r.test(s3)); // false

</script>

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零宽断言(?!exp)

反先行断言

什么是反先行断言，使用 (?!exp) 匹配后面跟的不是exp。

php实例：

主要是想通过实例给大家说下这个正则的作用

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$str="abcgwcab";

$parent='/bc(?!ww)gw/';

$str=preg_match($parent,$str,$match);

var_dump($str);

var_dump($match);

/**

输出：

int 1

array (size=1)

 0 => string 'bcgw' (length=4)

*/

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解析：首先判断字符串是否包含bc，然后判断其后面不是ww,最后匹配gw。可以看出反向断言之前后之后，能够在添加其他匹配条件。

.*?

这个.*就是匹配非空字符任意长度，?就是非贪婪模式就是匹配最少的字符例如一个字符

相信看了本文案例你已经掌握了方法，更多精彩请关注php中文网其它相关文章！

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正则全局匹配模式g修饰符的使用详解

正则表达式m修饰符(多行匹配)使用详解

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