ES6 vs ES2020 vs ESNext modules and which one should you use

The difference between ESNext, ES6/ES2015, ES2020, and other module options in TypeScript is mainly about which ECMAScript version’s module system is used. Here’s a breakdown:

1. "module": "ES6"

• Uses ESM (ECMAScript Modules) with import/export.
• Compiles to ES6 (ES2015) syntax.
• Works in modern browsers and newer Node.js versions.

Example:

TypeScript

export function greet() {
  console.log("Hello");
}

Output (JavaScript)

export function greet() {
  console.log("Hello");
}

Use this if you want to target older ES6-compatible environments.

2. "module": "ES2020"

• Uses ESM but allows dynamic imports (import()).
• Introduces features like BigInt, optional chaining (?.), and nullish coalescing (??).
• Good for modern JavaScript environments, including modern browsers and Node.js 14+.

Example of Dynamic Import:

TypeScript

async function loadModule() {
  const module = await import("./myModule");
  module.default();
}

Output (JavaScript)

async function loadModule() {
  const module = await import("./myModule.js");
  module.default();
}

Use this if you want better features but still maintain broad support.

3. "module": "ESNext"

• Uses the latest ECMAScript module features that TypeScript supports.
• Allows using newer JavaScript features that may not yet be standardized.
• Useful for projects that transpile code further (e.g., Babel, Webpack, ESBuild).
• Best suited for cutting-edge JavaScript environments (latest Node.js and modern browsers).

Use this if you want to future-proof your project and are okay with requiring recent JavaScript runtimes.

Which One Should You Use?

General Recommendation:

• For frontend projects (React, Next.js, Vue, etc.) → "module": "ESNext"
• For modern Node.js projects (ESM) → "module": "ESNext" or "ES2020"
• For libraries that need backward compatibility → "module": "ES2020"