# JavaScript ES6 教學

**ES6 = ECMAScript 6 = ECMAScript 2015.** 

ES6 還是未有直接support class的 private member.

當使用const/let等時, 且在node.js上, 則一定要運行在Strict Mode Code下, 即`use strict`. 不然會出現 Block-scoped declarations (let, const, function, class) not yet supported outside strict mode

### ES6 如何在class上模擬private data/method:

1. <http://www.2ality.com/2016/01/private-data-classes.html>
2. <http://stackoverflow.com/questions/27849064/how-to-implement-private-method-in-es6-class-with-traceur>

上述兩個link都提到兩種方式WeakMap & Symbol.

### ES6裡的Prototype

`class` 本質上是prototype的syntactical sugar)的導入. \[<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Inheritance_and_the_prototype_chain>]

Since ECMAScript 6, the \[\[Prototype]] is accessed using the accessors Object.getPrototypeOf() and Object.setPrototypeOf().

### let , const 為 block level 變數的關鍵字

```javascript
if(true){
  var x = 1;
}
console.log(x); //1

if(true){
  let y = 2; //its lifetime is only in thie scope     
}
console.log(y); //exception, undefined
```

### shorthand syntax of Method definitions

Given the following code:

```javascript
var obj = {
  foo: function() {},
  bar: function() {}
};
```

You are now able to shorten this to:

```javascript
var obj = {
  foo() {},
  bar() {}
};
```

## 其餘部份待補充, 可先參考

<https://github.com/lukehoban/es6features>

上面網站裡的功能清單 *ES6 includes the following new features*:

* [arrows](https://github.com/lukehoban/es6features/blob/master/README.md#arrows)
* [classes](https://github.com/lukehoban/es6features/blob/master/README.md#classes)
* [enhanced object literals](https://github.com/lukehoban/es6features/blob/master/README.md#enhanced-object-literals)
* [template strings](https://github.com/lukehoban/es6features/blob/master/README.md#template-strings)
* [destructuring](https://github.com/lukehoban/es6features/blob/master/README.md#destructuring)
* [default + rest + spread](https://github.com/lukehoban/es6features/blob/master/README.md#default--rest--spread)
* [let + const](https://github.com/lukehoban/es6features/blob/master/README.md#let--const)
* [iterators + for..of](https://github.com/lukehoban/es6features/blob/master/README.md#iterators--forof)
* [generators](https://github.com/lukehoban/es6features/blob/master/README.md#generators)
* [unicode](https://github.com/lukehoban/es6features/blob/master/README.md#unicode)
* [modules](https://github.com/lukehoban/es6features/blob/master/README.md#modules)
* [module loaders](https://github.com/lukehoban/es6features/blob/master/README.md#module-loaders)
* [map + set + weakmap + weakset](https://github.com/lukehoban/es6features/blob/master/README.md#map--set--weakmap--weakset)
* [proxies](https://github.com/lukehoban/es6features/blob/master/README.md#proxies)
* [symbols](https://github.com/lukehoban/es6features/blob/master/README.md#symbols)
* [subclassable built-ins](https://github.com/lukehoban/es6features/blob/master/README.md#subclassable-built-ins)
* [promises](https://github.com/lukehoban/es6features/blob/master/README.md#promises)
* [math + number + string + array + object APIs](https://github.com/lukehoban/es6features/blob/master/README.md#math--number--string--array--object-apis)
* [binary and octal literals](https://github.com/lukehoban/es6features/blob/master/README.md#binary-and-octal-literals)
* [reflect api](https://github.com/lukehoban/es6features/blob/master/README.md#reflect-api)
* [tail calls](https://github.com/lukehoban/es6features/blob/master/README.md#tail-calls)


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