gistfile1.js

function getKeys(obj, keys) {
    keys = keys || {};
    Object.keys(obj).forEach(function(k){
       if (!k in keys) {
           var o = obj[k];
           keys[k] = 1;
           if (typeof o === 'Object') {
               getKeys(o,keys);
           }
       }
    });
    return keys;
}