Run results for: For... in vs Spread

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/109.0

Browser: Firefox 109

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
for in	122023.8 Ops/sec
spread	93751.9 Ops/sec
for of	123065.8 Ops/sec

Script Preparation code:

function makeSpreadable(obj) {
    const proto = Object.getPrototypeOf(obj);
    const methods = Object.getOwnPropertyNames(proto);
    for (const method of methods) {
        if (method === "constructor") continue;
        obj[method] = proto[method];
    }
}

class Foo {
    constructor() {
        this.a = "";
        this.b = "";
        this.c = "";
        this.d = "";
        this.e = "";
        this.f = "";
        this.g = "";
        this.h = "";
        this.i = "";
        makeSpreadable(this);
    }

    doA() {}
    doB() {}
    doC() {}
    doD() {}
    doE() {}
    doF() {}
    doG() {}
    doH() {}
}

const foo = new Foo();
const bar = {};
for (const key in foo) {
    bar[key] = foo[key];
}

Tests:

for in
class Foo { constructor() { this.a = ""; this.b = ""; this.c = ""; this.d = ""; this.e = ""; this.f = ""; this.g = ""; this.h = ""; this.i = ""; } doA() {} doB() {} doC() {} doD() {} doE() {} doF() {} doG() {} doH() {} } const foo = new Foo(); const bar = {}; for (const key in foo){ bar[key] = foo[key]; }
spread
function makeSpreadable(obj) { const proto = Object.getPrototypeOf(obj); const methods = Object.getOwnPropertyNames(proto); for (const method of methods) { if (method === "constructor") continue; obj[method] = proto[method]; } } class Foo { constructor() { this.a = ""; this.b = ""; this.c = ""; this.d = ""; this.e = ""; this.f = ""; this.g = ""; this.h = ""; this.i = ""; makeSpreadable(this); } doA() {} doB() {} doC() {} doD() {} doE() {} doF() {} doG() {} doH() {} } const foo = new Foo(); const bar = {...foo};
for of
class Foo { constructor() { this.a = ""; this.b = ""; this.c = ""; this.d = ""; this.e = ""; this.f = ""; this.g = ""; this.h = ""; this.i = ""; } doA() {} doB() {} doC() {} doD() {} doE() {} doF() {} doG() {} doH() {} } const foo = new Foo(); const bar = {}; const props = Object.getOwnPropertyNames(foo); const proto = Object.getPrototypeOf(foo); const methods = Object.getOwnPropertyNames(proto); for (const key of props){ bar[key] = foo[key]; } for (const key of methods){ if (key === "constructor") continue; bar[key] = proto[key] }

Run results for: For... in vs Spread

for in

spread

for of