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Understanding $(document).ready() in jQuery

Understanding $(document).ready() in jQuery

To ensure an event works on your page, use the $(document).ready() function. This function loads everything inside it as soon as the DOM is ready, before the page contents are fully loaded.

Basic Usage

Here's how to use the $(document).ready() function to ensure your jQuery code runs when the document is ready:

$(document).ready(function() {
    // put all your jQuery code here
});

Advantages of $(document).ready()

The $(document).ready() function has several advantages:

  • Separation of Concerns: Keep your JavaScript/jQuery code in a separate file for better maintainability.
  • Inline JavaScript Avoidance: Avoid adding "behavioral" markup in the HTML, which keeps the HTML cleaner.
  • Multiple Functions: Unlike the onload attribute, which is limited to one function, $(document).ready() allows multiple functions.
  • Early Execution: Allows events to fire as soon as the DOM is registered by the browser.

Comparison with Traditional JavaScript

Traditional JavaScript often uses the onload attribute in the <body> tag, which has several drawbacks:

  • Adds "behavioral" markup to the content.
  • Limited to one function.
  • Triggers events when the window loads, not when the DOM is ready.

Jeremy Keith's book DOM Scripting explains how to create an addLoadEvent function for multiple functions, but it requires more code than the straightforward $(document).ready() method.

Conclusion

The $(document).ready() function in jQuery is a simple and effective way to execute code as soon as the DOM is fully loaded, providing benefits in terms of code organization, maintainability, and early execution.

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