JSFiddle - React, Tailwind, and code Playground

JavaScript

var url = 'http://w.soundcloud.com/player/?url=http%3A%2F%2Fapi.soundcloud.com%2Ftracks%2F85110490&auto_play=false&show_playcount=false&show_user=false&show_comments=false&buying=false&liking=false&sharing=false&show_artwork=false&color=00e7ff';

function soundcloudId(src) {
   var p = /http:\/\/w.soundcloud\.com\/.*%2Ftracks%2F([0-9A-F]+)/;
   return (src.match(p)) ? RegExp.$1 : false;
}

console.log(soundcloudId(url));