PHP empty in javascript

function empty (mixed_var) {
 // version: 909.322
 // discuss at: http://phpjs.org/functions/empty
 var key;
 if (mixed_var === "" || mixed_var === 0 || mixed_var === "0" || mixed_var === null || mixed_var === false || mixed_var === undefined ) {
  return true;
 }
 if (typeof mixed_var == 'object') {
  for (key in mixed_var) {
   return false;
  }
  return true;
 }
 return false;
}