[рони]

Trippal, не совсем понятно условие задачи ...

var options = {
     key1:"value1",
     key2:"value2",
     key3:{
              key31:"value31",
              key32:"value32"
     },
     key4:{
              key41:"value41",
              key42:"value42"
     }
}
function fn(obj, value)
{
  var elem = null;
  Object.keys(obj).forEach(function (key) {
	if(typeof obj[key] == "object") elem = fn(obj[key], value);
    else if (obj[key] == value) elem = obj;
});
return elem
}
var a = fn(options,"value42")
alert(JSON.stringify(a));