What is the diffence between object a and b ?

Question

var a = [];
a["name"] = "John";
a["age"] = 46;
document.write(a.name);

var b = {name: "umesh", age: 33}
document.write(b.name)

Answer 1

a's age is 46, b's age is 33.
a's name is "John", b's name is "umesh".

No other differences.

Answer 2

a.length = 0
b.length = undefined