Object.create と prototype を適切に使わない Class 定義が如何に遅いか

Aaa1.js

// function declaration
(function(global) {
"use strict";

function Aaa1(value) {
    this._value = value || "";
}

Aaa1.prototype = Object.create(Aaa1, {
    constructor:  { value: Aaa1 },
    value: {
        set: function(v) { this._value = v; },
        get: function()  { return this._value; }
    },
    concat:       { value: Aaa1_concat },
    concat$:      { value: Aaa1_concat$ },
});

function Aaa1_concat(a) { return this._value + a; }
function Aaa1_concat$(a) { this._value += a; return this; }

global["Aaa1"] = Aaa1;

})((this || 0).self || global);

Aaa2.js

// bad style
var Aaa2 = function(value) {
    "use strict";

    this._value = value || "";
    Object.defineProperties(this, {
        value: {
            set: function(v) { this._value = v; },
            get: function()  { return this._value; }
        }
    });
    this.concat = function(a) {
        return this._value + a;
    };
    this.concat$ = function(a) {
        this._value += a;
        return this;
    };
};

Aaa3.js

// defineProperties, function declaration
(function(global) {
"use strict";

function Aaa3(value) {
    this._value = value || "";

    Object.defineProperties(this, {
        value: {
            set: function(v) { this._value = v; },
            get: function()  { return this._value; }
        }
    });
}

Aaa3.prototype.concat  = Aaa1_concat;
Aaa3.prototype.concat$ = Aaa1_concat$;

function Aaa1_concat(a) { return this._value + a; }
function Aaa1_concat$(a) { this._value += a; return this; }

global["Aaa3"] = Aaa3;

})((this || 0).self || global);

Aaa4.js

// defineProperties, function expression
(function(global) {
"use strict";

function Aaa4(value) {
    this._value = value || "";

    Object.defineProperties(this, {
        value: {
            set: function(v) { this._value = v; },
            get: function()  { return this._value; }
        }
    });
}

Aaa4.prototype.concat  = function(a) { return this._value + a; };
Aaa4.prototype.concat$ = function(a) { this._value += a; return this; };

global["Aaa4"] = Aaa4;

})((this || 0).self || global);

Aaa5.js

// function expression
(function(global) {
"use strict";

function Aaa5(value) {
    this._value = value || "";
}

Aaa5.prototype = Object.create(Aaa5, {
    constructor:  { value: Aaa5 },
    value: {
        set: function(v) { this._value = v; },
        get: function()  { return this._value; }
    },
    concat:       { value: function(a) { return this._value + a; } },
    concat$:      { value: function(a) { this._value += a; return this; } },
});

global["Aaa5"] = Aaa5;

})((this || 0).self || global);

bad.class.style.md

• http://jsperf.com/codingstyle-and-heapmemory
• http://jsperf.com/webmodule-style-function-expression-vs-declaration