JavaScript中new运算符的实现过程解析

// 传参 New(obj, ...args)
function New() {
  let obj = new Object();
  // 提取第一个参数并作为构造函数;
  let construction = [].shift.call(arguments);
  // 新对象的__prop__要链接到原型链
  obj.__proto__ = construction.prototype;
  // 改变this指向
  construction.apply(obj, arguments);
  // 返回新对象
  return obj;
}

function People(name,age){
  this.name = name;
  this.age = age;
}
People.prototype.say = function () {
  console.log(`My name is ${this.name}.`);
}
//通过new创建构造实例
let people1 = new People('Jack',20);
console.log(people1.name)  // Jack
console.log(people1.say()) // My name is Jack.

//通过New方法创造实例
let people2 = New(People,'Rose',18);
console.log(people2.name)  //Rose
console.log(people2.say())  //My name is Rose.