Javascript 如何匹配字符 '<' 后面没有（'a' 或 'em' 或 'strong'）？
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How to match the character '<' not followed by ('a' or 'em' or 'strong')?
提问by Kyle
How would I make a regular expression to match the character <not followed by (aor emor strong)
我将如何做一个正则表达式匹配的字符<后面没有（a或em或strong）
So <helloand <stringwould match, but <strongwouldn't.
所以<hello和<string会匹配，但<strong不会。
回答by Andrew Hare
Try this:
尝试这个：
<(?!a|em|strong)
回答by cletus
You use a negative lookahead, the simplest form for which is (for this problem):
您使用了一个否定的 lookahead，最简单的形式是（对于这个问题）：
<(?!a|em|strong)
The one issue with that is that it will ignore <applet>. A way to deal with that is by using \b, which is a zero-width expression (meaning it captures none of the input) that matches a word to non-word or non-word to word transition. Word characters are [0-9a-zA-Z_]. So:
一个问题是它会忽略<applet>. 一种处理方法是使用\b，它是一个零宽度表达式（意味着它不捕获任何输入），它匹配单词到非单词或非单词到单词的转换。Word 字符是[0-9a-zA-Z_]. 所以：
<(?!(a|em|strong)\b)
回答by Antal Spector-Zabusky
If your regex engine supports it, use a negative lookahead assertion: this looks ahead in the string, and succeeds if it wouldn't match; however, it doesn't consume any input. Thus, you want /<(?!(?:a|em|strong)\b)/: match a <, then succeed if there isn't an a, em, or strongfollowed by a word break, \b.
如果您的正则表达式引擎支持它，请使用否定前瞻断言：这会在字符串中进行前瞻，如果不匹配则成功；但是，它不消耗任何输入。因此，你想 /<(?!(?:a|em|strong)\b)/：匹配A <，然后成功，如果没有一个a，em或者strong后面一个字突破，\b。
回答by WoodrowShigeru
Although Andrew's answer is clearly superior, before, I also got it to work with [^(?:a|em|strong)].
尽管安德鲁的回答显然更胜一筹，但在此之前，我也将其用于[^(?:a|em|strong)].
回答by SwiftNinjaPro
function strip_tags(str, keep){
if(keep && Array.isArray(keep)){keep = '|'+keep.join('|');}else if(keep){keep = '|'+keep;}else{keep = '';}
return str.replace(new RegExp('<\/?(?![^A-Za-z0-9_\-]'+keep+').*?>', 'g'), '');
}
usage:
用法：
strip_tags('<html><a href="a">a</a> <strong>strong text</strong> and <em>italic text</em></html>', ['strong', 'em']);
//output: a <strong>strong text</strong> and <em>italic text</em>
I would also recommend you strip parameters from the tags you keep
我还建议您从保留的标签中去除参数
function strip_params(str){
return str.replace(/<((?:[A-Za-z0-9_\-])).*?>/g, '<>');
}
