How to use JavaScript regex over multiple lines?

Question

var ss= "<pre>aaaa\nbbb\nccc</pre>ddd"; var arr= ss.match( /<pre.*?<\/pre>/gm ); alert(arr);     // null 

I'd want the PRE block be picked up, even though it spans over newline characters. I thought the 'm' flag does it. Does not.

Found the answer here before posting. SInce I thought I knew JavaScript (read three books, worked hours) and there wasn't an existing solution at SO, I'll dare to post anyways. throw stones here

So the solution is:

var ss= "<pre>aaaa\nbbb\nccc</pre>ddd"; var arr= ss.match( /<pre[\s\S]*?<\/pre>/gm ); alert(arr);     // <pre>...</pre> :) 

Does anyone have a less cryptic way?

Edit: this is a duplicate but since it's harder to find than mine, I don't remove.

It proposes [^] as a "multiline dot". What I still don't understand is why [.\n] does not work. Guess this is one of the sad parts of JavaScript..

Answer 1

DON'T use (.|[\r\n]) instead of . for multiline matching.

DO use [\s\S] instead of . for multiline matching

Also, avoid greediness where not needed by using *? or +? quantifier instead of * or +. This can have a huge performance impact.

See the benchmark I have made: http://jsperf.com/javascript-multiline-regexp-workarounds

Using [^]: fastest Using [\s\S]: 0.83% slower Using (.|\r|\n): 96% slower Using (.|[\r\n]): 96% slower 

NB: You can also use [^] but it is deprecated in the below comment.