Window.onload vs document.onload

Use case comparison

The speedy choice: DOMContentLoaded

Prefer DOMContentLoaded when your JavaScript needs the DOM ready, but not necessarily the images and style sheets. This allows your scripts to run faster, as the browser doesn't have to wait for assets to load.

Everything matters: window.onload

If your script relies on styled elements, images, or needs all frames to be fully loaded, window.onload is the obvious choice. This ensures all required resources are loaded for your script to execute flawlessly.

Understanding the details

Code Overwriting dilemma: window.addEventListener

Directly using window.onload can overwrite previously set onload events. Ensure a clean code structure by attaching events with addEventListener.

window.addEventListener('load', function() { /* Chef says, "All ingredients are in, let's cook!" */ });
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This allows adding multiple events without the fear of overwriting.

Time is of the essence: Timing issues

The DOMContentLoaded event mitigates timing issues from dynamically loaded scripts when used correctly with addEventListener. Performant and quick DOM-dependent concerns are well catered to.

Bye Bye jQuery

While $(document).ready() from jQuery seems handy, consider the performance gains and code visibility improvements from using plain JavaScript. A simple DOMContentLoaded with addEventListener() eliminates jQuery dependencies:

document.addEventListener('DOMContentLoaded', function() { /* Ready. Set. Go DOM! */) });
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Cross Browser Woes

Different browser behaviors for these events can lead to inconsistencies. Occasional console.log can help debugging and ensure your scripts are functional across all browsers. Remember, with great powers, comes great cross-browser compatibility responsibilities.