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