How to Use MutationObserver to Wait for nextElementSibling in JavaScript

Discover how to efficiently execute a function when a node's `nextElementSibling` exists using `MutationObserver`.
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Wait for nextElementSibling to Exist and Execute a Function

When developing dynamic web applications, you often encounter scenarios where elements are added to the DOM at unpredictable intervals. This can create complications when you need to run a specific function based on the existence of sibling elements. One common requirement is to determine when an element's nextElementSibling becomes available so that you can trigger functions that rely on this upcoming sibling element. In this post, we will explore a solution to wait for the existence of nextElementSibling and how to execute a function accordingly.

The Problem

You may have a situation where you have elements in the DOM, like the following:

[[See Video to Reveal this Text or Code Snippet]]

If a third-party script dynamically injects new elements such as:

[[See Video to Reveal this Text or Code Snippet]]

You might want to execute a function when these new elements appear. Specifically, you want to perform actions in a chain, triggering with each next sibling. For example:

When b has c, execute function X with c.

When c has d, execute function X with d, and so on.

Thus, the challenge is to efficiently wait for nextElementSibling to exist without relying on a simple CSS selector.

The Solution: MutationObserver

To tackle this issue, we can leverage the JavaScript MutationObserver API. This powerful API enables you to monitor DOM changes and execute a callback function when specific changes occur. Below is how you can create a function that awaits the nextElementSibling:

Step-by-Step Implementation

Define the Function:
You will create a function named waitForNextSibling that takes an element as an argument.

[[See Video to Reveal this Text or Code Snippet]]

Use the Function:
Here's how to use the waitForNextSibling function. You can call it with your element and then handle the resolved promise:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

With the provided waitForNextSibling function, you can seamlessly wait for nextElementSibling to exist, thus ensuring your functions are executed at the right time in a responsive and dynamic manner. Utilizing the MutationObserver API not only solves the problem effectively but also embraces modern best practices for dealing with DOM manipulations.

By applying this solution to your projects, you can ensure a smoother and more efficient user experience where elements appear and respond dynamically.

Feel free to implement this code in your own applications and tweak it as necessary to fit your specific needs!