SOURCE

function _new(fn, ...args) {
    if(typeof fn !== 'function') {
        throw Error('fn 必须是一个函数')
    }

    const p = Object.create(fn.prototype);

    const res = fn.call(p, ...args);

    if(res !== null && (typeof res === 'object')) {
        return res;
    }
    return p;
}

function B() {
    this.name = 'mike';
    
}
B.prototype.sayName = function() {
    console.log(this.name);
}

console.log(new B())

console.log(_new(B))

function _instanceof(target, source) {
    let t = Object.getPrototypeOf(target);
    while(t){
        if(t === source.prototype){
            return true;
        }
        t = Object.getPrototypeOf(t);
    }
    return false;
}
console.log(_instanceof(_new(B), B))
function C() {
    B.call(this);
    this.age = 12;
}
C.prototype = Object.create(B.prototype)
C.constructor = C;

console.log(new C())
console.log(_instanceof(_new(C), B))
console.log(_instanceof(Number(1), Number))
console.log(_instanceof([], Array))