Using an object as a property key in JavaScript

Question

What is going on in this code?

var a = {a:1};
var b = {b:2};
var c = {};

c[a] = 1;
c[b] === 1 // true!

c[b] = 2;
c[a] === 2 // true!

Spec

Answer 1

Why you use an object as a key, the key is becoming the object.toString() 's result which is [Object Object],

So what you are dothing is set a value to the property "[Object Object]", and get the value by the property "[Object Object]".