source
define two object both with getter and setter, with the same code
both test with benchmark.js in node v7.3.0
const builtInObject1 = (function (object) {
    let lastA = 1;
    return Object.defineProperties(object, {
        a:{
            get(){
                return lastA
            },
            set(newValue){
                lastA = newValue;
            }
        }
    })
})({});
const builtInObject2 = (function (object) {
    let lastA = 1;
    return Object.defineProperties(object, {
        a:{
            get(){
                return lastA
            },
            set(newValue){
                lastA = newValue;
            }
        }
    })
})({});
~ addes2015'sgetter/settercase
const builtInObject3 = (function () {
    let lastA = 1;
    return {
        get a(){
            return lastA
        },
        set a(value){
            lastA = value;
        }
    }
})();
~
const builtInObject4 = (function (object) {
    let last = 1;
    return Object.defineProperties(object, {
        b:{
            get(){
                return last
            },
            set(newValue){
                last = newValue;
            }
        }
    })
})({});
const builtInObject5 = (function (object) {
    let last = 1;
    return Object.defineProperties(object, {
        c:{
            get(){
                return last
            },
            set(newValue){
                last = newValue;
            }
        }
    })
})({});
~
(new Benchmark.Suite("object-assign-properties"))
    .add("#built-in object1.a getter and setter", function () {
        builtInObject1.a = builtInObject1.a + 1;
    })
    .add("#built-in object2.a getter and setter", function () {
        builtInObject2.a = builtInObject2.a + 1;
    })
    .add("#built-in object3.a es6 getter and setter", function () {
        builtInObject3.a = builtInObject3.a + 1;
    })
    .add("#built-in object4.b getter and setter", function () {
        builtInObject4.b = builtInObject4.b + 1;
    })
    .add("#built-in object5.c getter and setter", function () {
        builtInObject5.c = builtInObject5.c + 1;
    })
    .on('cycle', function(event) {
        console.log(String(event.target));
    })
    .on('complete', function() {
        console.log('Fastest is ' + this.filter('fastest').map('name'));
    })
    .run({ 'async': false });
result
#built-in object1.a getter and setter x 80,459,419 ops/sec ±0.65% (88 runs sampled)
#built-in object2.a getter and setter x 3,967,313 ops/sec ±0.36% (91 runs sampled)
#built-in object3.a es6 getter and setter x 3,982,725 ops/sec ±0.51% (93 runs sampled)
#built-in object4.b getter and setter x 79,608,022 ops/sec ±4.06% (87 runs sampled)
#built-in object5.c getter and setter x 78,849,808 ops/sec ±0.82% (92 runs sampled)
Fastest is #built-in object1.a getter and setter
difference between ops/sec of these tests result make me confuse
Why???
what makes these differences ?
accroding to bluebird | Optimization-killers, object3 would not be optimized, but why object2 get so slow ??
reference ???
- jsperf tests, seems both of two tests run with a optimized code in my browser (osx Chrome Canary 57, CPU:i7), just got 3,800,000opt/sec