javescript实现图片切换功能

<script>
 var i=1;
 var img = new Array();
 img[0] = "1.bmp";
 img[1] = "2.bmp";
 img[2] = "3.bmp";
 img[3] = "4.bmp";
 img[4] = "5.bmp";
 function playImg(){
  i=i+1;
  var imgs = document.getElementById("img");
  imgs.src =img[i];
  if(i>=4){
   i=1;
  }
 }
 window.onload = function(){
  document.getElementById("img").src="1.bmp";
 }
</script>
<img id="img" src="" width="500" hieght="500" onclick="playImg()" style="cursor:pointer;">