Prettier

3.8.3 · active · verified Sat Apr 18

Prettier is an opinionated code formatter that enforces a consistent style by parsing your code and re-printing it with its own rules, taking maximum line length into account. The current stable version is 3.8.3, and it receives frequent patch and minor releases, often including support for new language versions or bug fixes.

Common errors

```
Error: Prettier `format` functions must be passed a `parser` option or the file type must be detectable.
```
cause The `prettier.format()` function was called without a `parser` option and could not infer the language from the input.

fix Add a `parser` option to the format call, e.g., `prettier.format(code, { parser: 'babel' });`.
```
Error [ERR_REQUIRE_ESM]: require() of ES Module <path>/node_modules/prettier-plugin-xyz/index.mjs from <path>/node_modules/prettier/index.js not supported.
```
cause Attempting to load an ES Module (ESM) Prettier plugin using a CommonJS `require()` context. Prettier 3.x plugins must be ESM.

fix Ensure your project is set up to load ESM plugins correctly, or check that your plugin is compatible with Prettier 3.x's ESM-only plugin requirement. This might involve updating your `prettier.config.js` to be an ESM file or using `import` statements if your main config file is also ESM.
```
Cannot find module 'prettier'
```
cause The `prettier` package is not installed or not resolvable in the current project's `node_modules`.

fix Install Prettier using `npm install prettier` or `yarn add prettier`.
```
Error: Could not resolve a config for "...".
```
cause Prettier could not find a configuration file (e.g., `.prettierrc`, `prettier.config.js`) for the specified file path, or the configuration file is invalid.

fix Create a valid Prettier configuration file in the project root or specify options directly via CLI flags or API parameters.

Warnings

breaking Prettier 3.x requires Node.js version 14 or higher.
Fix: Upgrade your Node.js environment to version 14 or newer.
breaking Prettier 3.x plugins must be written as ES Modules (ESM). CommonJS plugins will fail to load.
Fix: Update custom plugins to ESM syntax or find updated plugin versions that support ESM. Your `prettier.config.js` might also need to be an ESM file (`.mjs` or `type: module` in `package.json`).
gotcha Prettier's opinionated formatting can lead to conflicts with existing manual style guides or other linters (e.g., ESLint).
Fix: Use specific integration packages like `eslint-config-prettier` to disable conflicting ESLint rules, and `eslint-plugin-prettier` to run Prettier as an ESLint rule.
gotcha When using the `format` API function, a `parser` option is often required if the input code's language cannot be automatically detected.
Fix: Always explicitly specify the `parser` option (e.g., `{ parser: 'babel' }` for JavaScript, `{ parser: 'typescript' }` for TypeScript) when calling `prettier.format()`.

Install

npm install prettier npm
yarn add prettier yarn
pnpm add prettier pnpm

Imports

prettier
```
import prettier from 'prettier';
```
Prettier 3.x core supports both ESM and CommonJS. For API usage, the main export `prettier` can be imported directly. Be aware that Prettier 3.x plugins must be ESM.

Quickstart

Formats a JavaScript string using Prettier's default rules, specifying the parser explicitly.

import { format } from 'prettier';

async function run() {
  const code = 'function   foo()   { return   "bar"; }';
  const formattedCode = await format(code, { parser: 'babel' });
  console.log(formattedCode);
  // Expected output:
  // function foo() {
  //   return "bar";
  // }
}
run();

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