title: JavaScript backslash (\) in variables is causing an error
body: <p>In Javascript, when I put a backslash in some variables like:</p>
  
  <pre><code>var ttt = "aa ///\\\";
  var ttt = "aa ///\"; 
  </code></pre>
  
  <p>Javascript shows an error.</p>
  
  <p>If I try to restrict user in entering this character, I also get an error:</p>
  
  <pre><code>(("aaa ///\\\").indexOf('"') != -1)
  </code></pre>
  
  <p>Restricting backslashes from user input is not a good strategy, because you have to show an annoying message to the user. </p>
  
  <p>Why am I getting an error with backslash?</p>