DOMContentLoaded vs. Load: When Should I Use Each Event?

DOMContentLoaded Event vs. Load Event: Key Differences

In web development, there are two crucial events, DOMContentLoaded and load, that play a significant role in page rendering and functionality. However, they differ in their timing and implications:

DOMContentLoaded Event

• Definition: Triggered when the HTML parser has loaded and parsed the entire HTML document, including its structure and content.
• Timing: Occurs before external resources (e.g., images, stylesheets) have fully loaded.

Load Event

• Definition: Triggered when the entire web page, including all external resources, has been fully loaded.
• Timing: Occurs after the DOMContentLoaded event and indicates that the page is ready for user interaction.

Summary of Differences

According to the Mozilla Developer Center, the primary difference between these events lies in their timing:

• DOMContentLoaded: Fired when the HTML content is loaded and accessible, before external resources load.
• Load: Fired when the entire web page, including external resources, has finished loading.

In practical terms, the DOMContentLoaded event is useful for tasks that do not require external resources, such as manipulating the page's structure or performing user interface operations. The load event is better suited for tasks that rely on external assets, such as loading images or initializing JavaScript modules that require access to the fully-loaded page.

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