JS当中构造原型链

function fn1(name,dress){          //fn1.prototype.__proto__:Object.prototype
			this.name=name,
			this.dress=dress
		}
		fn2.prototype=new fn1("南北","成都")//fn2.prototype.__proto__:fn1.prototype
		function fn2(age,post){
			this.age=age,
			this.post=post
		}
		fn3.prototype=new fn2(18,"teacher");//fn3.prototype.__proto__:fn2.prototype
		function fn3(habbit,edu){
			this.habbit=habbit,
			this.edu=edu
		}
		var sy=new fn3("listen to music","成都理工大学")//sy.__proto__:fn3.prototype
		
		console.log(sy.name);//南北
		
		console.log(sy.__proto__==fn3.prototype);//true
		console.log(fn3.prototype.__proto__==fn2.prototype);//true