关于JavaScript 中的switch 语句

//定义"改变颜色"的函数
    var count=0;
    var mytxt=document.getElementById("txt");
    function changeColor() {
       if(count===0)
       {
         txt.style.color="red";
         count++;
       }else if(count===1) {
           txt.style.color="orange";
           count++;
       }else if(count===2) {
           txt.style.color="yellow";
           count++;
       }else if(count===3) {
            txt.style.color="green";
            count++;
       }else if(count===4) {
            txt.style.color="cyan";
            count++;
       }else if(count===5) {
            txt.style.color="blue";
            count++;
       }else if(count===6) {
            txt.style.color="purple";
            count=0;
       }
       /*switch(count)
        {
            case 0
            {
               mytxt.style.display="none";
               txt.style.color="red";
               count++;
            }
            case 1
            {
                txt.style.color="orange";
                count++;
            }
            case 2
            {
                txt.style.color="yellow";
                count++;
            }
            case 3
            {
                txt.style.color="green";
                count++;
            }
            case 4
            {
                txt.style.color="cyan";
                count++;
            }
            case 5
            {
                txt.style.color="blue";
                count++;
                
            }
            case 6
            {
                txt.style.color="purple";
                count=0;
            }
            
        }*/

一开始想写个切换颜色的代码 , 习惯使用 switch , 结果不知道哪里出问题了 , 一直不能正常使用 ,但使用 if else 选择语句是可以实现功能的。 0.0 ~

刚学 Jsp 不是很熟练 , 求解惑 !