How do I match a number inside square brackets with regex

Question

I wrote a regular expression which I expect should work but it doesn't.

var regex = new RegExp('(?<=\[)[0-9]+(?=\])')

JavaScript is giving me the error：

Invalid regular expression :(/(?<=[)[0-9]+(?=])/): Invalid group

Does JavaScript not support lookahead or lookbehind?

Answer 1

This should work:

var regex = /\[[0-9]+\]/;

---

edit : with a grouping operator to target just the number:

 var regex = /\\[([0-9]+)\\]/;

With this expression, you could do something like this:

 var matches = someStringVar.match(regex); if (null != matches) { var num = matches[1]; }

Answer 2

Lookahead is supported, but not lookbehind. You can get close , with a bit of trickery.

Answer 3

To increment multiple numbers in the form of lets say:

var str = '/a/b/[123]/c/[4567]/[2]/69';

Try:

str.replace(/\[(\d+)\]/g, function(m, p1){
 return '['+(p1*1+1)+']' }
)

//Gives you => '/a/b/[124]/c/[4568]/[3]/69'

Answer 4

如果您要引用 RegExp，请注意双转义反斜杠。