var pet={    word:'...',    speak:function(say){        console.log(say+' '+this.word)    }}//pet.speak('speak')//speak ...var dog={    word:'wang'}//改变this到dog上pet.speak.call(dog,'speak')//spaeck wang

function pet1(word){    this.word=word;    this.speak=function(){        console.log(this.word)    }} //类似继承function dog1(word){    pet1.call(this,word);    //pet1.apply(this,arguments)}var dog1=new dog1('wang')dog1.speak()//wang