How to use variables in regular expressions in JavaScript.

regex-with-variables.js

function getURL(startMatch, endMatch, str) {
  var regex = new RegExp(startMatch + ': (.+), ' + endMatch);
  var contents = str.split(regex)[1];

  return contents ? contents : 'none found';
}

var str = 'website: http://www.google.com, soundcloud: http://www.soundcloud.com, facebook: http://www.facebook.com, stage: the main one';

console.log('Website URL:', getURL('website', 'soundcloud', str));
console.log('Soundcloud URL:', getURL('soundcloud', 'facebook', str));
console.log('Facebook URL:', getURL('facebook', 'stage', str));
console.log('Another URL:', getURL('this', 'that', str));

A video walkthrough is available here: https://youtu.be/9BVw7OOdqU4