Convert PHP RegEx to JavaScript RegEx

问题

I have a PHP regular expression I'm using to get the YouTube video code out of a URL.

I'd love to match this with a client-side regular expression in JavaScript. Can anyone tell me how to convert the following PHP regex to JavaScript?

preg_match("#(?<=v=)[a-zA-Z0-9-]+(?=&)|(?<=v\/)[^&\n]+(?=\?)|(?<=embed/)[^&\n]+|(?<=v=)[^&\n]+|(?<=youtu.be/)[^&\‌​n]+#", $url, $matches);

Much appreciated, thanks!

回答1:

I think the only problem is to get rid of the lookbehind assertions (?<=...), they are not supported in Javascript.

The advantage of them is, you can use them to ensure that a pattern is before something, but they are NOT included in the match.

So, you need to remove them, means change (?<=v=)[a-zA-Z0-9-]+(?=&) to v=[a-zA-Z0-9-]+(?=&), but now your match starts with "v=".

If you just need to validate and don't need the matched part, then its fine, you are done.

But if you need the part after v= then put instead the needed pattern into a capturing group and continue working with those captured values.

v=([a-zA-Z0-9-]+)(?=&)

You will then find the matched substring in $1 for the first group, $2 for the second, $3 ...

回答2:

you can replace your look behind assertion using this post

Javascript: negative lookbehind equivalent?

来源：https://stackoverflow.com/questions/9309349/convert-php-regex-to-javascript-regex