Object.freeze() perf hit in v8

freeze-perf.js

// A simple test to show the perf difference between property access
// in non-frozen, and frozen objects in v8
// `node freeze-perf.js`

var o1, o2, key, start;

o1 = {a: 1};
o2 = Object.freeze({a: 1});

start = Date.now();
for(var i=0; i<100000; i++) {
	for(key in o1) o1[key] = i;
}
console.log(Date.now() - start);

start = Date.now();
for(i=0; i<100000; i++) {
	for(key in o2) o2[key] = i;
}
console.log(Date.now() - start);

freeze-perf2.js

// A simple test to show the perf difference between property access
// in non-frozen, and frozen objects in v8
// `node freeze-perf2.js`

var o1, o2, start;

o1 = {a: 1};
o2 = Object.freeze({a: 1});

start = Date.now();
for(var i=0; i<1000000; i++) {
	o1.a = i;
}
console.log(Date.now() - start);

start = Date.now();
for(i=0; i<1000000; i++) {
	o2.a = i;
}
console.log(Date.now() - start);