类（class）:

class关键词：

let TestClass = class {};
const instance = new TestClass();

{class Inside {}}

typeof Inside // undefined: block scoped

方法与constructor：

class User {
constructor(id) {this.id = id;}

sayHello(){return ‘hello‘+this.id;}
}
const user = new User(42);

class Foo { constructor() { return Object.create(null); } }

getter setter：

class MyAccount {
get balance() { return this.amount; }

set balance(amount) { this.amount = amount; }
}

也可以这样：

const propertyName = ‘balance‘;
class MyAccount {
get [propertyName]() { return this.amount; }
set [propertyName](amount) { this.amount = amount; }
}

static：

const type = ‘test‘ + ‘Type‘;
class IntegrationTest {
static get [type]() { return ‘integration‘; } // static + get/set + 运行时命名
}

继承：

class A {}
class B extends A{}

function 定义的类也可以被继承：

let A = function (){};
class B extends A {}

isPrototypeOf:

class A {}
class B extends A {}

A.isPrototypeOf(B); // true

A.prototype.isPrototypeOf(new B()) // true

A.prototype.isPrototypeOf(B.prototype) // true

还可以：

let A;

class B extends (A = class {}) {}

class B extends (((beNull) => beNull ? null : class {})(true)) {}

super关键字：

普通方法与构造函数中使用super：

class A {iAmSuper() { return this.youAreSuper; }}
class B extends A {constructor() { super(); this.youAreSuper = true; } }
class C extends B {
iAmSuper() {
return super.iAmSuper();
}
}

class A {constructor(startValue=1, addTo=1) { this.counter = startValue + addTo; }}
class B extends A {
constructor(...args) {
super(...args);
this.counter++;
}
}

判断继承：

// not work for exends null, only for babel or ... ?

class A {hasSuper() { return super.constructor !== Object }}

class A {hasSuper() { return !super.constructor }}