1.当一个对象的内部状态发生改变时，会导致其行为的而改变，这看起来像是改变对象

对复杂的if else进行抽取

function showResult(result){
    if(result ==0){
        console.log(1);
    }else if(result ==1){
         console.log(2);
    }else if(result ==2){
         console.log(3);
    }

}
var Resutlstate= function(){
    var states = {
        state0: function(){
            console.log(1)
        },
        state1: function(){
            console.log(2)
        },
        state2: function(){
            console.log(3)
        },
        state3: function(){
            console.log(4)
        },
        state4: function(){
            console.log(5)
        }
    }
    function show(result){
        states['state'+ result] &&   states['state'+ result]();
    }
    return {
        show:show
    }
}