JavaScript Best Practices for Static HTML Pages
1. Use External Script Files (Linked Scripts)
Best practice: Yes ✅
Why:
- Keeps HTML clean and easier to maintain.
- Allows browser to cache JS files, improving performance on repeat visits.
- Supports separation of concerns (structure vs. behavior).
<script src="script.js" defer></script>2. Where to Place Scripts
Option A: Bottom of <body> (Legacy but Still OK)
<body>
...
<script src="script.js"></script>
</body>Option B (Modern Best Practice): Use defer in <head>
Why: Downloads script while parsing HTML, but delays execution until HTML is fully loaded.
<head>
<script src="script.js" defer></script>
</head>3. Avoid async Unless Needed
Use async only for independent scripts like analytics or ads.
Why not for critical scripts? It executes immediately when ready, potentially before the HTML is fully parsed.
<script src="analytics.js" async></script>4. Inline Scripts (Use Sparingly)
Why to avoid:
- Not reusable across pages.
- Harder to maintain and debug.
- Slows down page rendering if in the
<head>.
When OK: Very small, page-specific logic.
<script>
alert('Hello, world!');
</script>5. Minify Scripts in Production
Why:
- Reduces file size = faster load times.
- Removes comments and unnecessary whitespace.
Recommended tools: Terser, UglifyJS, Webpack, Vite, Rollup
6. Use Modern JavaScript Syntax
constandletinstead ofvar- Arrow functions:
() => {} - Template literals:
`Hello ${name}`
When: If not supporting very old browsers (e.g., IE11)
7. Use Module Scripts (Modern Option)
Why:
- Supports
import/exportsyntax. - Automatically defers execution.
- Scope is limited (no global pollution).
<script type="module" src="main.js"></script>✅ Summary Table
| Practice | Recommendation |
|---|---|
| External scripts | ✅ Yes |
defer in <head> |
✅ Yes |
| Inline scripts | ❌ Avoid unless very small |
async scripts |
⚠️ Only for independent/3rd party scripts |
| Minify scripts in production | ✅ Yes |
| Modern syntax & modules | ✅ Yes |
Created by ChatGPT · Updated for 2025 standards