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

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:

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

You are now able to shorten this to:

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
• classes
• enhanced object literals
• template strings
• destructuring
• default + rest + spread
• let + const
• iterators + for..of
• generators
• unicode
• modules
• module loaders
• map + set + weakmap + weakset
• proxies
• symbols
• subclassable built-ins
• promises
• math + number + string + array + object APIs
• binary and octal literals
• reflect api
• tail calls