javascript - XRegExp no look-behind? -

i need use lookbehind of regex in javascript, found simulating lookbehind in javascript (take 2). also, found author steven levithan 1 developed xregexp.

i git cloned xregexp 3.0.0-pre, , tested

some lookbehind logic http://regex101.com/r/xd0xz5 using xregexp

var xregexp = require('xregexp'); console.log(xregexp.replace('foobar', '(?<=foo)bar', 'test')); 

it seems not working;

$ node test foobar 

what miss? thanks.

edit: goal like

(?<=foo)[\s\s]+(?=bar) 

http://regex101.com/r/sv5gd5

(edit2 link wrong , modifed)

answer:

var str = "fooanythingbar"; console.log(str); console.log(str.replace(/(foo)(?:[\s\s]+(?=bar))/g, '$1test'));  //footestbar 

credit goes @trevor senior thanks!

it possible use non-capturing groups this, e.g.

$ node > 'foobar'.replace(/(foo)(?:bar)/g, '$1test') 'footest' 

in second parameter of string.replace, special notation of $1 references first capturing group, (foo) in case. using $1test, 1 can think of $1 placeholder first matching group. when expanded, becomes 'footest'.

for more in depth details on regular expression, view matches here.