title: Regex Always False multi Pattern
body: <p>I am facing a weird issue with Regex. My expression working fine in <a href="https://regexr.com/3cr6f" rel="nofollow noreferrer">https://regexr.com/3cr6f</a>
  But when i use the same expression in my code then it start failing.</p>
  <p>This is my Expression:</p>
  <pre><code>^([a-zA-Z]+\\)+(Documents){1}\\{1}((CT([A-Za-z]){0,2})|(FE)|(FF))$
  </code></pre>
  <p>I want to test this expression on my typescript string:</p>
  <pre><code> var case1='User\Folders\MyDocuments\CTTV';
   var case2='User\Folders\MyDocuments\FE';
   var case3='User\Folders\MyDocuments\FF';
  </code></pre>
  <p>But it always return me null.</p>
  <pre><code>var regex = new RegExp(/^([a-zA-Z]+\\)+(Documents){1}\\{1}((CT([A-Za-z]){0,2})|(FE)|(FF))$/);
  regex.test(case1); //false
  </code></pre>
  <p>Might be someone else also faced such issue in Javascript typescript.</p>