title: What does 'var that = this;' mean in JavaScript?
body: <p>In a JavaScript file I saw: </p>
  
  <pre><code>function Somefunction(){
     var that = this; 
     ... 
  }
  </code></pre>
  
  <p>What is the purpose of declaring <code>that</code> and assigning <code>this</code> this to it?  </p>