Question

我试图检查javascript（data [index]）中是否有未定义的内容，如果是，则显示警告。但是，它似乎没有打击。

我试过了：

  if(data[index]){ }

我试过了：

  if (typeof(jsVar) == 'undefined') { }

然而，它们似乎都不起作用，我得到了：

Uncaught ReferenceError: index is not defined

完整代码：

function myAlerts(data)
{
    $("#alertsListMissingPets").empty();
    $.mobile.loading( 'hide', { theme: "b", text: "Loading", textonly: false});
    if(data[index].Name){
    $.each(data, function(index) {
        console.log(data[index].LostDate)
        $("#alertsListMissingPets").append(" <li><a data-lostid='"+ data[index].LostKey + "' data-custom='"+ data[index].AnimalKey + "' href=\"#\">"+ data[index].Name + " <span class=\"ui-li-count\">"+ data[index].Distance + "</span></a></li>");
    });
    $("#alertsListMissingPets").listview('refresh');
    } else {
        function alertDismissed() {
            $.mobile.changePage("#mainpage");
        }
        navigator.notification.alert('No missing pets in your area!', alertDismissed, 'Good News', 'Okay' );
    }
}

Answer 1

显然，index未定义的错误状态。看看你的代码：

if(data[index].Name){ //Check something with index here
$.each(data, function(index) { //Define index here

您不能在循环外使用index ...

Answer 2

从错误索引变量可以看出未定义。您应该执行以下操作

typeof(index) == 'undefined'

或

typeof(index) != 'undefined'

Answer 3

正如其他海报的其他答案/评论中所述，您使用$ .each和数据[索引]定义并不正确。试试这个（未经测试）：

function myAlerts(data)
{
    $("#alertsListMissingPets").empty();
    $.mobile.loading( 'hide', { theme: "b", text: "Loading", textonly: false});
    if(data.length > 0) {
        $.each(data, function(value) { //index isn't needed based on your code
            $("#alertsListMissingPets").append(" <li><a data-lostid='"+ 
                value.LostKey + "' data-custom='"+ 
                value.AnimalKey + "' href=\"#\">"+ value.Name + 
                "<span class=\"ui-li-count\">"+ value.Distance + 
                "</span></a></li>");
        });
        $("#alertsListMissingPets").listview('refresh');
    } else {
        navigator.notification.alert('No missing pets in your area!', alertDismissed, 'Good News', 'Okay' );
    }
}

//moved this out of your else clause for aesthetics
function alertDismissed() {
    $.mobile.changePage("#mainpage");
}

检查未定义的javascript没有命中

3 个答案: