0 == false // true 
0 === false // false 
2 == "2" // true 
2 === "2" // false 

// example 
const val = "123"; 
if (val === 123) { 
  console.log(val); 
  // it cannot not be reached 
} 
if (val === "123") { 
  console.log(val); 
  // it can be reached
}

// 不推荐
let daysSLV = 10;
let y = new Date().getFullYear();
let ok;
if (user.age > 30) {
  ok = true;
}

//  推荐
const MAX_AGE = 30;
let daysSinceLastVisit = 10;
let currentYear = new Date().getFullYear();
...
const isUserOlderThanAllowed = user.age > MAX_AGE;

// 不要添加一些额外且不必要的词汇到你的变量名称中。

let nameValue;
let theProduct;

// 推荐
let name; 
let product;

function Person(name) {
  this.name = name;
}  


function Student(name) {  
  Person.call(this, name);
}

Student.prototype = Object.create(Person.prototype);
//  Student 的原型会被设置为 Person。

// 实际上想要将 Student 的原型设置为 Student。
// 需要这么写
Student.prototype.constructor = Student;

// 或者
class Student extends Person {
}

<script id="worker" type="javascript/worker">
  self.onmessage = (e) => {
    self.postMessage('msg');
  };
</script>
<script>
  const blob = new Blob([
    document.querySelector('#worker').textContent
  ]);

  const worker = new Worker(window.URL.createObjectURL(blob));
  worker.onmessage = (e) => {
    console.log(e.data);
  }
  worker.postMessage("hello");
</script>

//  不要这么写
['1','2','3'].map(parseInt)

// 可以
['1','2','3'].map(Number)
['1','2','3'].map(num => parseInt(num, 10))

// 当 x === 1 返回 false 不想调用 doSomethingElse 时
x === 1 ? doSomething() : doSomethingElse();

// 可以
x === 1 && doSomething();

yarn cache clear

const el = document.getElementById('foo');
el.textContent = 'foo';