title: When is null or undefined used in JavaScript?
body: <p>I am really confused as to when JavaScript returns <code>null</code> or <code>undefined</code>. Also different browsers seem to be returning these differently.</p>
  
  <p>Could you please give some examples of <code>null</code>/<code>undefined</code> with the browsers that return them.</p>
  
  <p>While I am now clear on the <code>undefined</code> aspect, I am still not 100% clear on <code>null</code>. Is it similar to a blank value?</p>
  
  <p>E.g. You have a text box which does not have any value set. Now when you try to access its value, will it be <code>null</code> or <code>undefined</code> and are they similar?</p>