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];
}