如何检查document.getElementbyId包含null或undefined值？

Question

if(typeof    (document.getElementById("courseId").value!=="undefined") || document.getElementById("courseId").value!==null)
    {
        Courseid = document.getElementById("courseId").value;
    } 

Answer 1

以这种方式重写它:

if(document.getElementById("courseId") && document.getElementById("courseId").value)
{
    CourseId = document.getElementById("courseId").value;
}