regex - How to use a Regular Expression in JavaScript which contains special characters -

sorry, being dumb morning, don't know regular expressions, have created want use https://regex101.com/

but... can't use code suggest in javascript without escaping first.

here's regex: (?<=color:\s)([a-z]+)

which, want (matching word after color: in css file)

but, code suggest use in js is:

var re = /(?<=color:\s)([a-z]+)/g;  var str = ' color: black'; var m;  while ((m = re.exec(str)) !== null) {     if (m.index === re.lastindex) {         re.lastindex++;     }     // view result using m-variable.     // eg m[0] etc. } 

the first line, won't work, escaped to: var re = /\(?<=color:\s\)([a-z]+)/i stops javascript error, won't match strings more.

what doing wrong?

as aside... can point me expanding regex exclude followed bracket? trying color names only, "color: black;" should match, "box-shadow: black... etc" should match, ideally, not "color: rgb(... etc"

it true js not support look-behinds, although there workarounds:

• reverse string , matches enables using look-aheads
• use capturing groups
• use while loop re.lastindex manipulation

in case, easier use capturing group:

var re = /\bcolor:\s*([a-z]+)/ig;   var str = ' color: black';  var m;    while ((m = re.exec(str)) !== null) {      if (m.index === re.lastindex) {          re.lastindex++;      }    // m[1] holding our value!       document.getelementbyid("res").innerhtml = m[1];  }

<div id="res"/>