js什么鬼？ 之 你真的懂吗？

promise then (...args) reduce Promise.resolve()

let applyAsync = (acc,val) => acc.then(val);
let composeAsync = (...funcs) => x => funcs.reduce(applyAsync, Promise.resolve(x));

for (let f of [func1, func2]) {
  await f();
}

来自：
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_promises

---

---

mozilla 上的一个关于闭包的例子

<p id="help">Helpful notes will appear here</p>
<p>E-mail: <input type="text" id="email" name="email"></p>
<p>Name: <input type="text" id="name" name="name"></p>
<p>Age: <input type="text" id="age" name="age"></p>

function showHelp(help) {
  document.getElementById('help').innerHTML = help;
}

function setupHelp() {
  var helpText = [
      {'id': 'email', 'help': 'Your e-mail address'},
      {'id': 'name', 'help': 'Your full name'},
      {'id': 'age', 'help': 'Your age (you must be over 16)'}
    ];

  for (var i = 0; i < helpText.length; i++) {
    var item = helpText[i];
    document.getElementById(item.id).onfocus = function() {
      showHelp(item.help);
    }
  }
}

setupHelp();

运行结果跟你想象的一样吗？
来自：
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures

---

---

这是一个用js执行多遍的回答，使用了ES6语法
https://stackoverflow.com/questions/30452263/is-there-a-mechanism-to-loop-x-times-in-es6-ecmascript-6-without-mutable-varia

const times = x => f => {
  if (x > 0) {
    f()
    times (x - 1) (f)
  }
}

// use it
times (3) (() => console.log('hi'))

// or define intermediate functions for reuse
let twice = times (2)

// twice the power !
twice (() => console.log('double vision'))

其实，我认为这种写法除了ES6语法的唬人，并没有什么好处，
因为，需要的栈空间与循环次数成正比。 从这方面讲，不如使用 for(var i=0;i<99;++i){ }

但是，可以作为一个学习ES6语法的好例子，看下图：

---

---

== 与 === 的区别

https://www.codecademy.com/en/forum_questions/558ea4f5e39efed371000508

---

---

TIM图片20180209141738.png

---

---