9.混入（用的不多）

// 混入对象1
class Bird {
    canFly: boolean;
    fly() {
        this.canFly = true;
        console.log('I can fly')
    }
}
// 混入对象2
class Fish {
    canSwim: boolean;
    swim() {
        this.canSwim = true;
        console.log('I can swim')
    } 
}
// 新对象
class FlyFish implements Bird, Fish {
    constructor() {}
    canFly:boolean= false;
    canSwim:boolean= false;
    fly: () => void;
    swim: () => void;
}
function doMixins(derivedCtor: any, baseCtors: any[]) {
    baseCtors.forEach(baseCtor => {
        Object.getOwnPropertyNames(baseCtor.prototype).forEach(name => {
            derivedCtor.prototype[name] = baseCtor.prototype[name];
        });
    });
} 
doMixins(FlyFish, [Bird, Fish]);
let flyFish = new FlyFish();
console.log(flyFish.canFly);
flyFish.swim();