// 原本的 function

let fn = function(){

  console.log(this.constructor.name);  // Object(data)

  setTimeout(function(){

    console.log(this.constructor.name) // Window

  },100);

}

​

// 箭頭函示 Arrow function

let fn_arr = function(){

  console.log(this.constructor.name);  // Object(data)

  setTimeout(() => {

    console.log(this.constructor.name) // Object(data)

  },100);

}

​

let id = 21;

let data = {

  id: 21

}

​

fn.call(data);     // Window

fn_arr.call(data); // Object(data)

​

​