JSFiddle - React, Tailwind, and code Playground

HTML

<pre id="xx">
</pre>

JavaScript

var rgbString =  "rgb(0, 70, 255)";
var RGBAString = "rgba(0, 70, 255, 0.5)";
var noMatch = "rgb(0, 70, 255, 0.5)";

var rgbRegex = /(^rgb\((\d+),\s*(\d+),\s*(\d+)\)$)|(^rgba\((\d+),\s*(\d+),\s*(\d+)(,\s*\d+\.\d+)*\)$)/; 

var partsRGB = rgbString.match(rgbRegex); 
var partsRGBA = RGBAString.match(rgbRegex);
var noMatchRes = noMatch.match(rgbRegex);

var el = document.getElementById("xx");
el.innerHTML += partsRGB + "\n";
el.innerHTML += partsRGBA+ "\n";
el.innerHTML += noMatchRes + "\n";