[11 | JS 02] A Beginner’s Guide to JavaScript Versions: ES5, ES6+, and ESNext

JavaScript has come a long way since it was first created in 1995. If you're learning JavaScript today, you might hear terms like ES5, ES6, or ESNext and wonder what they mean. In this article, we’ll walk through the history of JavaScript versions and explain how to use modern JavaScript features today, without breaking your code or worrying about browser support.

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🕰️ A Brief History of JavaScript

• 1995 – Brendan Eich creates JavaScript in just 10 days. It was initially named Mocha, later LiveScript, and finally JavaScript (to ride the popularity of Java, even though the two are unrelated).
• 1996 – Microsoft adds its own version called JScript in Internet Explorer.
• 1997 – To avoid chaos, the language is standardized under the name ECMAScript, and ES1 becomes the first official version.
• 2009 – ES5 (ECMAScript 5) is released with many important improvements.
• 2015 – ES6 (also called ES2015) brings the biggest upgrade ever. From here, ECMAScript moves to a yearly release cycle.
• 2016–present – New versions are released every year (e.g., ES2016, ES2017, ..., ES2024, and so on).

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🧩 ECMAScript vs JavaScript

• ECMAScript (ES): The official specification of the language.
• JavaScript: The actual implementation used in browsers and other environments.

Think of ECMAScript as the blueprint, and JavaScript as the working building based on that blueprint.

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🔁 Backward Compatibility: "Don't Break the Web!"

One of the core principles of JavaScript is backward compatibility:

• Older features are never removed.
• Updates are incremental (not full rewrites).
• This ensures that old websites keep working forever.

So, when we say “new version,” it usually means a set of new features added, not a major overhaul.

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🧑‍💻 How to Use Modern JavaScript Today

🧪 During Development

• Use the latest version of Google Chrome, Firefox, or another modern browser. They support most modern features.

🚀 During Production

• Use Babel (a JavaScript compiler) to:

  • Transpile new syntax into older JavaScript (ES5).
  • Polyfill features that don’t exist in older browsers (like Promise, Array.prototype.includes).

This makes sure your code runs smoothly for all users.

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📦 ES5, ES6+, and ESNext Explained

✅ ES5 (ECMAScript 5) – Released in 2009

• Fully supported in all major browsers (even IE9, released in 2011).
• You can use ES5 without any transpiling today.

✨ ES6 / ES2015 and Beyond (ES6+) – Released in 2015 and later

• Introduced major features like:

  • let, const
  • Arrow functions (() => {})
  • Template literals (`Hello, ${name}!`)
  • Destructuring
  • Classes
  • Modules (import, export)
  • Promises

• Mostly supported in modern browsers, but not in older ones.

• Use Babel for backward compatibility.

🔮 ESNext – The Future

• Refers to future versions of JavaScript (anything after ES2021).
• Features go through a multi-stage proposal process. Once they reach Stage 4, they’re officially added to the language.

• Examples of recent or upcoming features:

  • ?. (Optional chaining)
  • ?? (Nullish coalescing)
  • Array.prototype.at()
  • Promise.withResolvers() (in ES2024)

• Can often be used with polyfills and transpiling even before full browser support.

To check what features are supported in which browsers, visit:
👉 Kangax Compatibility Table

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🧠 Should You Still Learn Old JavaScript?

Yes. And here’s why:

1. Understand how JavaScript works under the hood.
2. Lots of online tutorials and legacy code are still written in ES5.
3. You may work on older codebases at some point.

Understanding both modern and traditional JavaScript will make you a stronger developer.

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✅ Summary

Version	Year	Browser Support	Use in Production?	Key Features
ES5	2009	Fully supported (IE9+)	✅ Yes	strict mode, forEach, Object.keys(), etc.
ES6+	2015+	Modern browsers only	✅ With Babel	let, const, arrow functions, classes, etc.
ESNext	2021+	Varies	✅ With Babel	Optional chaining, logical assignment, etc.

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✍ Final Thoughts

If you're starting to learn JavaScript in 2025, start with modern ES6+ features, but don't skip the basics of ES5. Use tools like Babel to write modern code today while ensuring compatibility for everyone. And keep an eye on ESNext features. These are shaping the future of the language!

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📬 Let’s Connect
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💼 LinkedIn: Anik Paul
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