CODEWITHSUNDEEP
c#javascript
Brunodeluk
Brunodeluk

Reputation: 47

getelementbyid().length undefined?

I have this code in C#:

 @foreach (var photo in photos){
            <div class="comment1" id="many">
             @photo.name
            </div>
}
<input type="button" name="button" onclick="count()" />

And I want to know how many "photo.names's" there are, so I made this javascript

function count(){
var algo = document.getElementById("many");
alert(algo.length);
}

But for some strange reason it gives me "undefined". Why is it happening? I have the javascript on a separate file

Upvotes: 0

Views: 4272

Answers (2)

poke
poke

Reputation: 387567

document.getElementById, as the method name suggest, gets a single element, not multiple.

Ids in HTML are supposed to be unique; there should be only one element with an id. So getElementById returns exactly that element.

If you want to mark multiple items, you should use a class name instead. You can then use document.getElementsByClassName.

Upvotes: 1

Kodlee Yin
Kodlee Yin

Reputation: 1089

Why is it happening?

HTML elements do not have a length property. If you're looking for the length of what the element contains you'd need to do this

document.getElementById("many").innerHTML.length;

Keep in mind that IDs should be unique to an element.

If you're looking for "how many" comments there are, you'd need to do the following

document.getElementsByClassName("comment1").length;

Classes don't need to be unique across elements and and element can have more than 1 class.

Upvotes: 3

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