window.onload = function (){ var oLi = document.getElementById("tab").getElementsByTagName("li"); var oUl = document.getElementById("content").getElementsByTagName("ul"); for(var i = 0; i < oLi.length; i++) { oLi[i].index = i; oLi[i].onmouseover = function () { for(var n = 0; n < oLi.length; n++) oLi[n].className=""; this.className = "current"; for(var n = 0; n < oUl.length; n++) oUl[n].style.display = "none"; oUl[this.index].style.display = "block" } }}想請問下，oLi[i].index = i; 給遍歷的li標簽都附上 下標編號的意義是什么，為啥oUl[this.index].style.display = "block"中oUI對象要用[this.index]來表示要改變的是哪個ul標簽，為什么不能用循環里定義的i變量？？是因為作用域的問題嗎？