how can find array value in jquery?

I want check if array contain some value i do something, but this code can't find array contains

 var randArray = {};
   $.post("postpon.php", 
      function(response){
         var data = jQuery.parseJSON(response);
         var count = 1; 
         $.each(data, function(key, value) {
            randArray[count] = value[0];
            count++;
         })
     // if (randArray.contain())
     //  {
              // do something
     //  }

   })