javascript - 排除未定义的值

Question

每隔一段时间我就会看到一个 <li>undefined</li>我如何让它不循环未定义的 <li> ？

function relatedCoursesMesh() {
    if ($('#relatedCourses').length != 0) {
        var courseNumber = $.parseHTML($('#relatedCourses #RelatedCourseNumber').html()),
            courseName = $.parseHTML($('#relatedCourses #RelatedCourseName').html()),
            parsedCourseNumber = courseNumber[0].data.split("+"),
            parsedCourseName = courseName[0].data.split("+");


        htmlOutput = "<ul>";

        $(parsedCourseNumber).each(function (index, val) {

            htmlOutput += '<li><a data-course="' + val + '" data-title="' + parsedCourseName[index] + '" href="/Pages/Class.aspx?course=' + val + '&courseTitle=' + parsedCourseName[index] + '" title="Related Course">' + parsedCourseName[index] + '</a></li>';
        })
        htmlOutput += "</ul>";
        $('#relatedCourses').html(htmlOutput);
    }
} 

Answer 1

您可以像这样放置 if 语句:

    $(parsedCourseNumber).each(function (index, val) {
        if(parsedCourseName[index]) { // also ignores "" (blank) and null values
            htmlOutput += '<li><a data-course="' + val + '" data-title="' + parsedCourseName[index] + '" href="/Pages/Class.aspx?course=' + val + '&courseTitle=' + parsedCourseName[index] + '" title="Related Course">' + parsedCourseName[index] + '</a></li>';
        }
    })