example.js

var foo, bar;

class Aaa {
    constructor(a, b) {
        this.a = a;
        this.b = b;
    }
}

class Bbb {
    constructor(fn) {
        fn(this);
    }

    static make(init) {
        const obj = new this();
        if (init) init(obj);
        return obj;
    }
}

class Ccc {
    static make(init) {
        const obj = new this();
        if (init) init(obj);
        return obj;
    }
}

function abc() {
    for (let j = 0; j < 1e7; j++) {
        var x = new Aaa(() => foo, () => bar);
    }
    return x;
}

function abc2() {
    for (let j = 0; j < 1e7; j++) {
        var x = new Bbb(obj => {
            (obj.a = () => foo), (obj.b = () => bar);
        });
    }
    return x;
}
function abc3() {
    for (let j = 0; j < 1e7; j++) {
        var x = Ccc.make(obj => {
            (obj.a = () => foo), (obj.b = () => bar);
        });
    }
    return x;
}

var x = new Bbb(obj => {});
var x = new Bbb(obj => {});
var x = new Bbb(obj => {});
var x = new Bbb(obj => {});

var x = Ccc.make(obj => {});
var x = Ccc.make(obj => {});
var x = Ccc.make(obj => {});
var x = Ccc.make(obj => {});

console.time('perf');
abc();
console.timeEnd('perf');

console.time('perf');
abc2();
console.timeEnd('perf');

console.time('perf');
abc3();
console.timeEnd('perf');