未捕獲的TypeError：無法讀取未定義的屬性x

Question

在實際腳本正常工作並生成正確的輸出的同時，在Chrome控制台中出現上述錯誤，想知道如何擺脫該錯誤以及導致該錯誤的原因。

JSFiddle： http : //jsfiddle.net/wJUeP/

HTML代碼：

<ul id="menu"></ul>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>

JS代碼：

$(function(){
var data = [{"weekending":"09\/10\/2013","jobs":[{"jobnumber":"1001","jobaddress":"Test1001","employees":[{"employeenumber":"1","name":"James Blabla","class":"FHM","notes":"xx","nt-wkmon":"2","t12-wkmon":"5","dt-wkmon":"4","status-wkmon":"Public Holiday","startTime-wkmon":"4","finishTime-wkmon":"6","nt-wktue":"7"}]},{"jobnumber":"1002","jobaddress":"Test1002","employees":[{"employeenumber":"1","name":"Cameron Le","class":"FHQ","notes":"xx","nt-wkmon":"2","t12-wkmon":"5","dt-wkmon":"4","status-wkmon":"Public Holiday","startTime-wkmon":"4","finishTime-wkmon":"6","nt-wktue":"7"},{"employeenumber":"2","name":"David Le","class":"FHQ","notes":"xx","nt-wkmon":"2","t12-wkmon":"5","dt-wkmon":"4","status-wkmon":"Public Holiday","startTime-wkmon":"4","finishTime-wkmon":"6","nt-wktue":"7"}]},{"jobnumber":"1003","jobaddress":"Test1003","employees":[{"employeenumber":"1","name":"Nick G","class":"sdf","notes":"sdf","nt-wkmon":"2","t12-wkmon":"5","dt-wkmon":"4","status-wkmon":"Public Holiday","startTime-wkmon":"4","finishTime-wkmon":"6","nt-wktue":"7"}]}]}];

for(var i = 0, j = data[0].weekending.length; i<j; i++) {
    rootMenu = data[0].jobs[i];
    $("#menu").append("<li id='job_" + rootMenu.jobnumber + "'>" + rootMenu.jobnumber);
    if(rootMenu.hasOwnProperty("employees")) {
        $("#menu").append("<ul id='employees_job_" + rootMenu.jobnumber + "'>");
        for(var n = 0, m = rootMenu.employees.length; n<m; n++) {
            var subMenu = rootMenu.employees[n];
            if(subMenu.hasOwnProperty("name")) {
                $("#employees_job_" + rootMenu.jobnumber).append("<li>" + subMenu.name + "</li>");
            }
        }
        $("#menu").append("</ul>");
    } else {
        $("#menu").append("</li>");
    }
}
});

注意：我仍處於應用程序的開發階段，可以靈活地更改和操作數據結構，如果嵌入式JSON數據看起來很糟糕，我可以對其進行更改，實際數據存儲在XML文件中，然后由PHP讀取並輸出為JSON。

Answer 1

for循環條件不正確。

您使用了j = data[0].weekending.length ，它等於10，並且要遍歷只有3個作業的data[0].jobs對象。 您遍歷了作業3次以上，因此收到錯誤。

檢出提琴http://jsfiddle.net/wJUeP/7/

Answer 2

錯誤在這里：

j = data[0].weekending.length

這將返回10，這是周末屬性== 10（“ 09/10/2013”​​）中字符串的長度，我想您需要此：

j = data[0].jobs.length