Why Does Getelementbyid Not Work on Elements Inside the Document Element

Why does getElementById not work on elements inside the document element?

Container IDs should be unique, so there's no reason to find an object by ID within another container. This is why you only need document.getElementById to access any element by its ID, whereas when you are searching by class or tag name, you might want to only search within a specific container, which is why you can do x.getElementsByClassName etc.

Why getElementById does not work on elements other than document?

getElementById is a method of document, not of document.body. The same goes for getElementsByName.

On the other hand, getElementByTagName and getElementByClassName can be called on any element including body.

document.getElementById not behaving as expected

A <template>'s children don't get rendered - they aren't really on the page. As MDN says:

Think of a template as a content fragment that is being stored for subsequent use in the document. While the parser does process the contents of the <template> element while loading the page, it does so only to ensure that those contents are valid; the element's contents are not rendered, however.

It doesn't have children in the DOM.

console.log(document.querySelector('template').children.length);
<template>
<p>foo</p>
</template>

unable to use getElementById on HTML element not yet appended to document

From MDN documentation for Document.getElementsByClassName:

  • getElementsByClassName can be called on any element, not only on the document. The element on which it is called will be used as the root of the search.

https://developer.mozilla.org/en-US/docs/Web/API/Document/getElementsByClassName

Document.getElementById does not have that note: https://developer.mozilla.org/en-US/docs/Web/API/Document/getElementById

The difference is that getElementsByClassName seems to be inherited by NodeLists from Document whereas getElementById is not. The reason I assume is that getElementsByClassName returns what it is working on , which is a NodeList or HTMLCollection, thus allowing for chainability; whereas getElementById will always return zero or one Nodes or HTMLElements.

document.getElementById not working?

Element doesn't have getElementById method, document has,

so use

document.getElementById('slide');

Javascript, GetElementById element is not defined?

From your code above it shows that you're trying to call a method getElementById() which you have not yet defined.

2ndly, you can only assign only 1 id in a document else it will not work.

you can do something like this

// i want to display this with javascript, after the login

<span id="coupon" style="display: none">
<h1>You won giftcard </strong></h1>
<button>abas</button>
</span>

what you meant to call is document.getElementById("coupon"); which is the right function to do.

so try this;

var zzz = document.getElementById("coupon");

i don't really know what your criteria is for a successful login but this show help
let say you set a variable as var success = "yes" on successful login

if(success === "yes"){
zzz.style.display = "block";
}

Why document.getElementById() command doesn't work on my code?

You need to use innerText, textContent or innerHTML instead of value.

Why can't I call getElementById on a javascript element?

You appear to have a couple issues.

  1. divBox.getElementById("divID"); doesn't work because getElementById() is only a method on the document object. It is not a method on other types of objects. So, the divBox element does not have that method. You could use document.getElementById("divID") instead if there was only one divID in the entire document and if divBox was already inserted into the document.

  2. var divContents = divBox.getElementsByClassName("divClass")[0]; works because .getElementsByClassName() is a method on all DOM objects so it works when you call it on divBox.

You call getElementById() like this document.getElementById("someID").

If you want to find something in a particular part of the subtree, you can use element.querySelectorAll("#someID") or if you want to have more than one object with a given identifier, then you can use a class name and use functions that find objects with a given class name.

As to your specific questions:

divBox.getElementById is not a function

That is because geetElementById() is only a method on the document object and divBox is not a document object so it does not have that method, therefore you get the error you are seeing.

Why does this have no issue:?

var divContents = divBox.getElementsByClassName("divClass")[0];

That is apparently because divClass is a class name, not an id value and all HTML elements contain the getElementsByClassName() method so you can call it on divBox just fine.



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