JavaScript: new 后发生了什么

[xvno]

No description provided.

[xvno]

在这里考虑如下几条

• Fn 作为某个类的构造函数
• neu() 作为关键字new的别名函数
  则有

let fn = neu(Fn); // fn = new Fn();

neu的实现:

function neu (Fn) {
  if(typeof Fn !== 'function') {
    throw new TypeError('Not a constructor');
  }
  let obj = {};
  let result = Fn.call(obj);

  let type = typeof result;
  if(type === 'object' || type === 'function') {
    obj = result
  }
  Object.setPrototypeOf(obj, Fn.prototype);
  return obj;
}