Jquery: Why use document.ready if external JS at bottom of page?

javascript

prompt-engineering

best-practices

web-development

byAnton Shumikhin·Dec 5, 2024

Using $(document).ready() safeguards code execution until after the DOM is fully initialized, even if your JavaScript is located at the end of the body tag. This matters profoundly if you're manipulating elements with jQuery which might be pending initialization due to still-loading dependencies like images or CSS. It ensures safe, error-free DOM manipulation:

$(document).ready(function() {
  // The DOM walks into a bar and...boom! It's ready to party here!
});

It's a safeguard for the entire DOM-dependent script universe to prevent errors and deliver a superior user experience.

`$(document).ready()`: A necessity or an option?

Positioning your JavaScript at the bottom of the page can ensure initial DOM readiness when your script runs. But, $(document).ready() brings an extra level of certainty, adding predictability and reliability. Here's a breakdown:

Browser compatibility

Not all browsers, especially legacy ones, ensure that JS executes after DOM loading. The .ready() method helps maintain consistency across browsers.

Asynchronous elements

Elements like images or iframes might load after the DOM is parsed. This is where $(document).ready() can provide a safety net for DOM-dependent codes.

Codebase clarity

$(document).ready() explicitly communicates to other devs that the code is meant to run post-DOM loading. It’s a nod to readability and maintainability.

A practical guide to `$(document).ready()`

$(document).ready() isn’t just about error prevention; it's a confidence booster when developing. But when does it truly shine?

Loading content dynamically

When loading content dynamically through AJAX or handling templates, $(document).ready() ensures that you’re not left grasping in the dark.

Fragmented scripts

In a modular project with scripts distributed across various files, wrapping your jQuery code in $(document).ready() ensures seamless dependency management.

Third-party scripts

$(document).ready() gives you some control over when your dependant codes run, even when third-party scripts are loaded asynchronously.

Trade-offs and exceptions

While deploying $(document).ready() contributes to safe web development, direct method calls can sometimes be faster in case of small, uncomplicated scripts.

Skip `$(document).ready()` when:

Dealing with a minimalist static page with no or few external resources
Writing script just below the DOM elements it manipulates
Employing modern development techniques, like building with Web Components

Your alternatives to `$(document).ready()`

Ever-growing JavaScript has blessed us with alternatives such as DOMContentLoaded and load events. These native events control script execution without needing jQuery.

DOMContentLoaded

This event shoots off when the initial HTML document has been loaded and parsed, without waiting for stylesheets, images, and iframes to complete loading.