js多重继承

方法一：克隆一个A对象，再将 B 对象的属性混入，适用于 A/B 的属性不冲突的场景；

function mixInto(object, mixIn){
    forEachIn(mixIn, function(name, value){
        object[name] = value;
        });
};

var SmallDetailedItem = clone(DetailedItem);
mixInto(SmallDetailedItem, SmallItem);

var deadMouse = SmallDetailedItem.create("Fred the mouse", "he is dead");

方法二：用 A 对象扩展一个子对象，再用 B 对象 扩展并覆盖子对象中的冲突属性；

var Monster = Item.extend({
	construct: function(name, dangerous){
		Item.construct.call(this, name);
		this.dangerous = dangerous;
	},
	kick: function(){
		if (this.dangerous){
			alert(this.name + " bites your head off");
		}
		else{
			alert(this.name + " squeaks and runs away");
		}
	}
});

var DetailedMonster = DetailedItem.extend({
	construct: function(name, description, dangerous){
		DetailedItem.construct.call(this, name, dangerous);
		Monster.construct.call(this, name, dangerous);
	},
	kick: Monster.kick
});

var giantSloth = DetailedMonster.create(
	"the giant sloth",
	"it is quietly hanging from a tree, munching leaves",
	false);
	
giantSloth.kick();