fragment的使用

var fragment = document.createDocumentFragment(),
  input = null,
  arr = new Array("postionX","postionY","relativeDiv"),
  length=arr.length,
  i;
  arr=arr.reverse();
  for (i=length-1; i > -1; i--){
    input = document.createElement("input");
    input.id=arr[i];
    input.name=arr[i];
    input.value="";
    input.type="hidden";
    fragment.appendChild(input);
  }            
document.body.appendChild(fragment);