根据各种来源（2ality，esdiscuss），应该可以将mixins添加到类中：
编辑发现类方法不可枚举，因此无法工作。编辑了下面的代码，但仍然没有快乐
class CartoonCharacter {
constructor(author) {
this.author = author;
}
drawnBy() {
console.log("drawn by", this.author);
}
}
// THIS CANNOT WORK
// class methods are not enumerable
// class Human {
// haveFun() {
// console.log("drinking beer");
// }
// }
let Human = Object.create({}, {
haveFun: {
enumerable: true,
value: function () {
console.log("drinking beer");
}
}
});
class Simpson extends Object.assign(CartoonCharacter, Human) {
constructor(author) {
super(author);
}
}
let homer = new Simpson("Matt Groening");
homer.drawnBy(); // expected: drawn by Matt Groening
homer.haveFun(); // expected: drinking beer
我得到了Matt Groening＆＃34;而不是喝啤酒＆＃34;我收到错误
-> Uncaught TypeError: E.haveFun is not a function
答案 0 :(得分：14)
你的mixins有两个问题：
Object.assign仅复制对象的可枚举属性。但是，类的方法和属性是不可枚举的。这是使用mixins扩展类的方法：
class CartoonCharacter {
constructor(author) {
this.author = author;
}
drawnBy() {
console.log("drawn by", this.author);
}
}
class Human {
haveFun() {
console.log("drinking beer");
}
}
mixin(CartoonCharacter, Human);
class Simpson extends CartoonCharacter {
constructor(author) {
super(author);
}
}
let homer = new Simpson("Matt Groening");
homer.drawnBy(); // expected: drawn by Matt Groening
homer.haveFun(); // expected: drinking beer
function mixin(target, source) {
target = target.prototype; source = source.prototype;
Object.getOwnPropertyNames(source).forEach(function (name) {
if (name !== "constructor") Object.defineProperty(target, name,
Object.getOwnPropertyDescriptor(source, name));
});
}
它在Babel中的预期效果如下：demo。
答案 1 :(得分：14)
还有另一种在Javascript中实现mixins的方法：使用子类工厂。
子类工厂是一个除了基类并返回该基类的扩展子类的函数：
const mixin = base => class extends base {
/* properties to mix in */
}
子类工厂可能有两个原因：
class es可以定义为表达式，是Javascript中的第一类* extends子句可以包含任意表达式让我们应用这种模式：
// superclass
class CartoonCharacter {
constructor(author) { this.author = author }
drawnBy() { return "drawn by " + this.author }
}
// mixin 1
const Human = base => class extends base {
haveFun() { return "drinking beer" }
}
// mixin 2
const Simpson = base => class extends base {}
// composed subclass
const Homer = Simpson(Human(CartoonCharacter));
// create an instance
const homer = new Homer("Matt Groening")
console.log(homer.drawnBy());
console.log(homer.haveFun());
sublcass工厂使用mixins有什么好处？
Human / Simpson）和子类（Homer）可以照常使用super
class CartoonCharacter {
constructor(author) { this.author = author }
drawnBy() { return "drawn by " + this.author }
}
const Human = base => class extends base {
haveFun() { return "drinking beer" }
}
const Simpson = base => class extends base {
constructor(arg, ...superArgs) {
super(...superArgs);
this.name = arg;
}
sayHey() { return "Hey, I am " + this.name }
}
const Homer = Simpson(Human(CartoonCharacter));
const homer = new Homer("Homer Simpson", "Matt Groening")
console.log(homer.drawnBy());
console.log(homer.haveFun());
console.log(homer.sayHey());
*术语第一类函数意味着函数可以作为参数传递或返回值，如普通数据
答案 2 :(得分：0)
正如@mfeineis，@ aadit-m-shah和@gotofritz以及@ftor的最新帖子所展示的那样，人们总是需要仔细考虑巫师类去 cripple < / em>成为一个“mixin”，而不是如何（重新）将它们组装成一个仍然可以被认为是一个好设计的层次结构。这些例子只是表明，JavaScript可能需要比我们已经（强制）使用的更接近特征的东西。有点像...
ApplicableType的申请时间执行。为了在实践中证明这样一个概念，我确实将所有上述例子重构为 trait from trait 的组合，并从对象组成来自类构造函数中的traits 。
我想讨论这种方法，它的优点和缺点，与目前使用的所有已经被接受的技术相比。
// - stateful applicable object/type proxy that does
// link `this` context and injected local state.
//
const withExposeInternalStateProxy = Trait.create(function (use, applicator) {
applicator(function (stateValue) {
this.valueOf = function valueOf () {
return Object.assign({}, stateValue);
};
this.toString = function toString () {
return JSON.stringify(stateValue);
};
});
});
// - applicable object/type that just implements plain behavior.
// - also known as: function based mixin ... kind of "FLight Mixin reloaded".
//
const withHumanBehavior = Trait.create(function (use, applicator) {
function allowWeekness() {
return "allow weekness";
}
function showStrength() {
return "show strength";
}
function thinkFirst() {
return "think first";
}
function drinkingBeer() {
return "drinking beer";
}
applicator(function () {
this.allowWeekness = allowWeekness;
this.showStrength = showStrength;
this.thinkFirst = thinkFirst;
this.drinkingBeer = drinkingBeer;
});
});
// - composite trait that uses its trait composition language ... trait from trait(s).
//
const withStrongBeerDrinkingHabit = Trait.create(function (use, applicator) {
use(withHumanBehavior)
.apply(withHumanBehavior, "drinkingBeer").as("haveFun");
//.apply.all.without("thinkFirst");
//.apply(withHumanBehavior).without("thinkFirst");
});
// - trait that defines a specialized use case of another behavior.
//
const withDoAcceptAlreadyExistingDrinkingHabit = Trait.create(function (use, applicator) {
applicator(function () {
var
type = this;
if (typeof type.haveFun !== "function") {
withStrongBeerDrinkingHabit.call(type);
}
});
});
class CartoonCharacter {
constructor(stateValue) {
// linking `this` context and injected local state.
withExposeInternalStateProxy.call(this, stateValue);
}
drawnBy() {
return ("drawn by " + this.valueOf().author);
}
}
class MaleSimpsonsType extends CartoonCharacter {
constructor(stateValue) {
super(stateValue);
// object/type composition
//
withDoAcceptAlreadyExistingDrinkingHabit.call(super.constructor.prototype);
// withStrongBeerDrinkingHabit.call(super.constructor.prototype); // do not always apply.
//
// withStrongBeerDrinkingHabit.call(this); // nope ...prototype is the far better choice.
}
sayHey() {
return ("Hey, I am " + this.valueOf().name);
}
}
const homer = new MaleSimpsonsType({ name: "Homer Simpson", author: "Matt Groening" });
console.log("\n");
console.log('(homer + "") : ', (homer + ""));
console.log('homer.valueOf() : ', homer.valueOf());
console.log("\n");
console.log('homer.drawnBy() : ', homer.drawnBy());
console.log('homer.haveFun() : ', homer.haveFun());
console.log('homer.sayHey() : ', homer.sayHey());
console.log("\n");
console.log('Object.keys(homer) : ', Object.keys(homer));
console.log('homer.constructor : ', homer.constructor);
console.log('Object.keys(homer.constructor.prototype) : ', Object.keys(homer.constructor.prototype));
console.log('homer.constructor.prototype : ', homer.constructor.prototype);
console.log('(homer instanceof MaleSimpsonsType) : ', (homer instanceof MaleSimpsonsType));
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对于备份上面的例子，还有另一个线程 - Refactoring legacy mixin-based class hierarchies - 我也有机会重构OP给出的例子。这个功能对基于普通对象的行为进行了after和around修改。这里使用的方法/工具集确实符合OP的所有要求。现在可以使用类，免费获取封装的状态/数据，并且对任何类型的方法修改都有状态支持。