title: Populate data to multiple html Dropdown list from a JSON file using jquery or Ajax
body: <p>I have three dropdown list. By default the values of all  three are "All". By this value the second and thrid dropdown list will be disabled with "ALL" value. when we change the value of first dropdown list, the second list will be enabled and populte the sub categories related to  the category selected on the first list. when we change the value of second list (by default it is "All"), thethird list is enabled and populate the sub categories of the category of second list. all the values are taken from a JSON file: it's in the format</p>
  
  <pre><code>var accounts = ["WHDH","TF"];
  
  
  var mediaGroups = {"WHDH": ["WHDH_1","WHDH_2"], "TF": ["TF_1","TF_2"]};
  
  
  var clipUrls = {"WHDH_1": ["/live/whdh1/1","/live/whdh1/2","/live/whdh1/3"], "WHDH_2": ["/live/whdh2/1","/live/whdh2/2","/live/whdh2/3"], "TF_1": ["/live/tf1/1","/live/tf1/2","/live/tf1/3"], "TF_2": ["/live/tf2/1","/live/tf2/2","/live/tf2/3"]};
  </code></pre>
  
  <p>The first list is Account, second is Media Groups, Thrid is Clip URLS.</p>