title: How do the regular expressions in sizzle.js work?
body: <p>If escaped characters in a regular expression created in JavaScript with the RegExp object need to be escaped again how does the following code in sizzle.js work - </p>
  
  <pre><code>identifier = "(?:\\\\.|[\\w-]|[^\0-\\xa0])+"
  </code></pre>
  
  <p>If <code>\\\\\\\ = \</code> and <code>\\\w = \w</code> then how does <code>\0 = \0</code> when only a single backslash is used?</p>
  
  <p>When run in Google console <code>identifier</code> is <code>"(?:\\\\.|[\w-]|[^-\\xa0])+"</code></p>
  
  <p>Is this a mistake or am I not understanding correctly? If this is correct and this is how it is intended to work what is the purpose of <code>\0</code>?</p>