`window.onload` or `document.onload`: Which Event Listener Has Broader Browser Support?

Which Event Listener is More Extensively Backed: window.onload or document.onload?

When selecting an event listener for page load detection, it is crucial to consider browser compatibility.

window.onload and document.onload: Firing Differences

• window.onload: Originally intended to trigger upon the complete loading of a webpage (including images, CSS, and scripts), it now also serves as a replacement for document.onload in some modern browsers, firing when the DOM is ready.
• document.onload: Specifically fires once the DOM is ready, typically prior to the loading of images and other external content.

Browser Support Comparison

window.onload appears to enjoy wider browser support. In fact, several cutting-edge browsers have effectively replaced document.onload with window.onload.

Addressing Browsers with Limited Support

To combat compatibility concerns, many developers are migrating to libraries like jQuery for this purpose, as it automatically checks for document readiness, as seen in the below code samples:

$(document).ready(function() { /* code here */ });
$(function() { /* code here */ });

Historical Context: window.onload vs body.onload

In a similar historical debate, window.onload was favored over body.onload due to the notion of separating structure from action. This encouraged the separation of the document's HTML markup from the handling of onLoad events.

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