élément las de l'objet

var fruitObject = { 'a' : 'apple', 'b' : 'banana', 'c' : 'carrot' };
Object.keys(fruitObject); // this returns all properties in an array ["a", "b", "c"]
fruitObject[Object.keys(fruitObject)[Object.keys(fruitObject).length - 1]] // "carrot"
Bored Beaver