Where the best place to put JavaScript?

Table of Contents

Introduction

The best place to put JavaScript depends on how and when you want the script to execute. JavaScript can be placed in:

  • The **<head>** section
  • The bottom of **<body>**
  • External JavaScript files

Each approach has pros and cons. Let’s explore the best practices for placing JavaScript in an HTML document.

1. Placing JavaScript in the <head> Section

Best for: Scripts that must load before the page content (e.g., analytics, tracking codes).
Downside: Blocks HTML rendering if the script is large.

Example: JavaScript in <head>

  • The script runs before loading the page content.
  • It may slow down page rendering.

Best Practice:

If placing JavaScript in <head>, use the **defer** or **async** attribute:

  • **defer**: Ensures scripts run after the page is loaded.
  • **async**: Runs scripts as soon as downloaded (useful for independent scripts like analytics).

2. Placing JavaScript at the End of <body> (Recommended)

Best for: Improving page load speed.
Ensures that the HTML is fully loaded before JavaScript runs.

Example: JavaScript at the Bottom of <body>

  • The script runs after the page loads, avoiding rendering delays.
  • Recommended for most cases.

3. Using External JavaScript Files (Best for Maintainability)

Best for: Keeping code organized and reusable.
Improves performance by enabling browser caching.

Example: External JavaScript File (script.js)

HTML File:

script.js File:

  • Keeps JavaScript separate from HTML, making it easier to manage.

Best Practice: Use defer when linking external JavaScript

  • Ensures JavaScript loads without blocking the HTML.

Conclusion: Best Placement for JavaScript

Use **<head>** only for small scripts or with **defer/async**.
Best practice: Place JavaScript at the end of **<body>** to improve page speed.
Use external JavaScript files for better maintainability and performance.

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