Question

为什么我会收到：未捕获的TypeError：无法读取属性＆lt; innerHTML＆＃39;未定义？我想从一个＆＃34;任务＆＃34;获得日，月和年。所以我可以计算出任务剩余的天数，但我得到了这个错误。

<div class="task" id="task">
                <ul>
                    <li class="title" id="@ta.Id"><div class="complete"></div>@ta.Title</li>
                    <li class="body"><b>Project: </b>@ta.Description</li>
                    <li>Hand In: @ta.Dia/@ta.Mes/@ta.Año</li>
                    <li class="leftion">Days left: </li>
                    <li class="day" style="display: none">@ta.Day</li>
                    <li class="month" style="display: none">@ta.Month</li>
                    <li class="year" style="display: none">@ta.Year</li>
                </ul>
            </div>
<script language="javascript" type="text/javascript">
var today = new Date();
     var dd = today.getDate();
     var mm = today.getMonth() + 1; //January is 0!

     var yyyy = today.getFullYear();
     if (dd < 10) {
         dd = '0' + dd
     }
     if (mm < 10) {
         mm = '0' + mm
     }
     var firstDate = new Date(yyyy, mm, dd);
     var gio = document.getElementsByClassName("task");
     var lele = document.getElementsByClassName("leftion");
     for (var i = 0; i <= gio.length; i++) {
         var oneDay = 24 * 60 * 60 * 1000; // hours*minutes*seconds*milliseconds
         var day= document.getElementsByClassName("day")[i].innerHTML;

未捕获的TypeError：无法读取属性＆lt; innerHTML＆＃39;未定义的

        var month = document.getElementsByClassName("month")[i].innerHTML;
        var year= document.getElementsByClassName("year")[i].innerHTML;
         var secondDate = new Date(year, month, day);


         var diffDays = Math.round(Math.abs((firstDate.getTime() - secondDate.getTime()) / (oneDay)));
         lele[i].innerHTML = diffDays;
     }
</script>

Answer 1

您的html

中可能有.task个节点而不是.day个节点

如果您只在当前.task节点的节点中查找当天，您将有更多机会找到您的错误并避免许多奇怪的行为：

var gio = document.getElementsByClassName("task");
//...
for (var i = 0; i <= gio.length; i++) {
    //...
    var taskNode = gio[i];
    var day = taskNode.getElementsByClassName("day")[0].innerHTML;

请参阅gio[i].getElementsByClassName的使用，而不是document.getElementsByClassName

Answer 2

使用循环for (var i = 0; i <= gio.length; i++) {...}时，gio.length === 1，这意味着循环将运行两次。

因此，当i === 1时，document.getElementsByClassName("day")[i]为undefined，因为您只有一天＆＃34;天＆＃34; class element。

将i <= gio.length更改为i < gio.length或一般重构代码。

Javascript - 无法读取属性＆inner;内部HTML＆＃39;未定义的

2 个答案: