Does $(document).ready() Always Have Access to Final CSS Values?

Are CSS Values Available When $(document).ready() Executes?

Question:

Why does a script执行于$(document).ready on a page with dynamic content alignment sometimes lag or malfunction?

Answer:

According to jQuery's release notes and documentation, $(document).ready() may not wait for CSS values to be fully injected into the DOM. Therefore, it is recommended to include all CSS files in the before any script references.

Explanation:

1. Asynchronous CSS Loading: CSS files are loaded asynchronously, meaning JavaScript can execute before CSS rendering is complete.
2. CSS Dependency on JS Calculations: In some cases, JavaScript calculations rely on CSS values to determine element dimensions and positioning, which can lead to inaccuracies if CSS values are not yet available.

3. Browser-Specific Behavior: The behavior observed in the asked question may be related to specific browser behaviors, such as:

   • Internet Explorer: Sometimes halts JS execution until external CSS is loaded, especially if CSS is placed above JS in the page.
   • Other browsers: May not always halt JS execution even if CSS is not fully loaded.

Resolution:

To ensure CSS values are available when $(document).ready() executes:

1. Always include CSS files before JavaScript references in the of the HTML document.
2. If possible, consider moving the script to the bottom of the page, after all CSS and content has loaded.

Additional Notes:

• In most cases, placing CSS above JS will resolve performance issues related to CSS dependency on JS calculations.
• However, complex browser-specific behaviors related to asynchronous resource loading and script execution may still occur.

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