<script>
test_obj = {a:1, b:2};
console.log(test_obj);

test_obj['aa'] = 11;
test_obj.bb = 22;
console.log(test_obj);

delete test_obj.a;
delete test_obj['b'];
console.log(test_obj);
</script>

Object {a: 1, b: 2}
Object {a: 1, b: 2, aa: 11, bb: 22}
Object {aa: 11, bb: 22}