Describe the difference between `<script>`, `<script async>` and `<script defer>` for Optimal Website Performance

Ever wondered how to optimize JavaScript loading on your web pages? The answer lies in understanding the different ways to include scripts using the <script> tag. Here's a breakdown:

1. <script> (Default):

• Blocks HTML parsing until the script is downloaded and executed.
• Use this for critical scripts that the page relies on to render initially.

2. <script async>:

• Downloads the script in parallel with HTML parsing.
• Executes the script as soon as it's available, potentially before HTML parsing finishes.
• Order of execution isn't guaranteed.
• Ideal for non-critical scripts like analytics that don't depend on the DOM being fully built.

3. <script defer>:

• Downloads the script in parallel with HTML parsing.
• Waits for the HTML to be fully parsed before executing the script, but before the DOMContentLoaded event fires.
• Scripts execute in the order they appear in the HTML.
• Use this for scripts that rely on the DOM being fully available, like manipulating page elements.

Key Takeaways:

• async for independent, non-critical scripts.
• defer for DOM-dependent scripts that preserve order.
• Both improve performance by allowing parallel parsing.
• Not for critical rendering scripts!

Bonus Tip: Avoid document.write() with async or defer scripts.

By understanding these options, you can ensure your website loads faster and delivers a smoother user experience!