regex - JavaScript regular expression exception (Invalid group)

Question

I have the following regular expression:

/(?<={index:)d+(?=})/g

I am trying to find index integer in strings like this one:

some text{index:1}{id:2}{value:3}

That expression works fine with php, but it doesn't work in javascript, I get the following error:

Uncaught SyntaxError: Invalid regular expression: /(?<={index:)d+(?=})/: Invalid group

What do I need to fix?

Thanks.

Answer 1

(?<= ) is a positive lookbehind. JavaScript's flavor of RegEx does not support lookbehinds (but it does support lookaheads).