how to check document.getElementbyId contains null or undefined value in it?

Question

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

http://stackoverflow.com/questions/801032/why-is-null-an-object-and-whats-the-difference-compared-to-undefined?rq=1 — Marvin Emil Brach, Jun 20 '13 at 07:43
OP is clearly a new user of SO and perhaps was not used to finding duplicate questions. It looks like a very reasonable question to me. Were all those downvotes actually necessary? — port5432, Oct 30 '15 at 10:32
I don't think this question is a duplicate since it's clearly asking about the type of a value in an input. — Shayan, Mar 03 '19 at 15:30

score 9 · Accepted Answer · answered Jun 20 '13 at 07:41

9

rewrite it that way:

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

answered Jun 20 '13 at 07:41

Marco Forberg

2,617
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fine working thanks a lot mate!!! – Matrix Jun 20 '13 at 08:25

score 2 · Answer 2 · answered Jun 20 '13 at 07:43

2

If you explicitly want to check for undefined and null you can do

if(document.getElementById('courseId') === null || 
   document.getElementById('courseId') === undefined) {
    //logic
}

answered Jun 20 '13 at 07:43

glosrob

6,547
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score 0 · Answer 3 · answered Jun 20 '13 at 07:43

0

An input's value will never be null or undefined - it will be the empty string, "".

answered Jun 20 '13 at 07:43

Eric

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`document.getElementById("myInput").value.typeof` returns `undefined` for me. Even when I assign a value to it by typing in the input box like typing `20` it still returns `undefined`. – Shayan Mar 03 '19 at 15:22

how to check document.getElementbyId contains null or undefined value in it?

3 Answers3