编辑代码

function myNew(fn, ...params) {
    let obj = Object.create(fn.prototype);
    const res = fn.apply(obj, params);
    if (res && (typeof res === 'object' || typeof res === 'function')) {
        return res;
    }
    return obj;
}

function App() {
    this.a = 1;
}

const res = myNew(App);

console.log(res);