JavaScript知识点
[ES6新特性](https://www.jianshu.com/p/87008f4f8513?tdsourcetag=s_pcqq_aiomsg)
let与const声明变量，他们是块级作用域：
```js
function getClothing(isCold) {
if (isCold) {
const freezing = 'Grab a jacket!';
} else {
const hot = 'It's a shorts kind of day.';
console.log(freezing);
}
}
```
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