How to Verify Element Existence in the Visible DOM Without Relying on getElementById

How to Determine the Existence of an Element in the Visible DOM

You may face scenarios where you need to verify an element's presence without relying on the getElementById method. This article discusses an improved approach and provides insights into the behavior of JavaScript variables.

Custom Function for Element Existence Check

As demonstrated in the provided code, retrieving an element into a variable does not guarantee a live reference to the DOM. To accurately check for existence, you can employ a function like isNull(). This function assigns a random ID to the element, retrieves it using the assigned ID, and then removes the ID to avoid side effects.

Alternative Methods

Besides this custom function, there are more straightforward options for checking element existence:

• Browser Selection Methods: Techniques like document.getElementById("find-me") or similar methods that return a reference to the element or null can be used. For a Boolean result, apply !! before the method call.
• Other Element Selection Methods: document offers several methods for finding elements, such as querySelector(), getElementsByClassName(), and more. Verify their length properties as some methods (like NodeList) return truthy values even when empty.

Visible DOM Check

To specifically check if an element resides in the visible DOM, utilize the contains() method on DOM elements:

document.body.contains(someReferenceToADomElement);

This method provides a more precise existence verification.

Understanding JavaScript Variable Behavior

Regarding why JavaScript variables display the observed behavior, the explanation lies in the nature of variables. Consider the code:

var myVar = document.getElementById("myElem");

myVar stores a reference to the element, not a live connection to it. When the element is removed from the DOM, its reference pointer within myVar is not updated. Thus, typeof myVar remains "object" and isNull(myVar) returns false, indicating apparent element presence despite its removal.

By understanding these concepts, you can effectively verify element existence in various DOM scenarios.

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