When is jQuery\'s `document.ready` Function Absolutely Necessary?

When Is jQuery's document.ready Function Essential?

jQuery's document.ready function is designed to execute code when the DOM is completely loaded and ready for manipulation. Its primary purpose is to ensure that code targeting DOM elements is only run when they are accessible.

Usage Guidelines:

• DOM Manipulation: Always wrap code that accesses DOM elements (e.g., using selectors, event handlers) within $(document).ready.
• Initialization of Plugins: Plugins that interact with the DOM should also be initialized within document.ready.
• AJAX Event Handling: .on() click handlers can be placed outside document.ready if they target dynamically created elements within it. Otherwise, they should be placed inside.

Performance and Scope Considerations:

• Performance: The performance difference between keeping objects inside or outside document.ready is generally negligible.
• Object Scope: Objects declared within document.ready are only accessible within that scope. When an AJAX-loaded page requests external resources, they can only access objects defined outside document.ready (truly "global" objects).

Best Practices:

• Place all your JavaScript/jQuery code (library and app code) at the bottom of the HTML page.
• Use the defer attribute on jQuery-containing scripts in AJAX-loaded pages to ensure library availability.
• Consider wrapping code that accesses the DOM in $(document).ready, even if it's placed at the bottom, to ensure consistency.

By following these guidelines, you can effectively leverage jQuery's document.ready function to ensure smooth DOM interaction and maintain a clean and performant codebase.

The above is the detailed content of When is jQuery\'s `document.ready` Function Absolutely Necessary?. For more information, please follow other related articles on the PHP Chinese website!