JavaScript Formatter
Formatters & BeautifiersBeautify JavaScript, TypeScript, JSX with Prettier-style formatting. Free, private — all processing in your browser.
The JavaScript Formatter beautifies messy, minified, or inconsistent JavaScript code following Prettier-compatible rules. Works with plain JavaScript (ES5 through ES2024), TypeScript (.ts, .tsx), JSX/TSX (React components), Node.js code, and module systems (CommonJS, ESM). Configurable formatting: indentation (2 spaces default, 4 or tab), quote style (single, double, backtick for specific cases), semicolons (required or optional), trailing commas (none, ES5, all), line width (80 default, customizable for wider screens), and bracket spacing.
Consistent code formatting is foundational for team collaboration. Without it, every developer writes JavaScript slightly differently — inconsistent indentation, mixed quotes, missing semicolons — making code reviews about style rather than substance. This formatter applies industry-standard Prettier rules so your code matches the de facto JavaScript style used by most modern projects (React, Vue, Next.js, etc.). Perfect for cleaning up legacy code, formatting minified output for debugging, or normalizing code from different sources before committing to a shared repository.
JavaScript Formatter — key features
Prettier-compatible output
Uses same rules as industry-standard Prettier. Output matches what your team expects.
Multi-language support
JavaScript, TypeScript, JSX, TSX. Automatic detection or manual selection.
Configurable style
Indentation, quote style, semicolons, trailing commas, line width — match your project.
JSX formatting
React components formatted with props on separate lines for long elements, children indented properly.
Modern syntax support
ES2022+ features, optional chaining, nullish coalescing, private class fields.
Handles minified code
Expand minified production code back to readable format.
Preserves comments
Line and block comments kept in original positions.
100% client-side
Your code (possibly proprietary business logic) stays in browser.
How to use the JavaScript Formatter
- 1
Paste JavaScript/TypeScript
Source code from file, clipboard, or typed directly.
- 2
Select language
JavaScript, TypeScript, JSX, TSX — auto-detected but manually selectable.
- 3
Configure style
2 vs 4 spaces, single vs double quotes, with/without semicolons. Match project conventions.
- 4
Click Format
Beautified code appears instantly.
- 5
Copy or download
Copy to clipboard or download as .js / .ts / .jsx / .tsx file.
Common use cases for the JavaScript Formatter
Team development
- →Normalize team code: Different developers write differently. Run through formatter to normalize.
- →Prepare code for PR: Format before committing so reviewers focus on logic, not style.
- →Migrate to Prettier: Existing codebase adopting Prettier — format everything first, then enable in CI.
Debugging
- →Read minified production JS: Expand minified code to understand what is happening in production bugs.
- →Inspect bundled code: Webpack/Vite output is minified. Format to read what your app ships.
- →Understand third-party libraries: Format vendor code to understand library internals.
Learning and teaching
- →Readable code examples: Format code snippets for tutorials, documentation, blog posts.
- →Learn style conventions: See how professional code is formatted.
- →Compare personal style to Prettier: Format your code to learn how Prettier thinks about JS.
Quick tasks
- →Format code from Stack Overflow: SO answers often have inconsistent formatting. Clean up before using.
- →Clean up Copilot/ChatGPT output: AI-generated code may not match your team style. Format to normalize.
- →Pre-commit formatting: If you do not have editor integration, paste through this tool before committing.
JavaScript Formatter — examples
Basic formatting
Messy to clean.
function hello(name){console.log(`Hello, ${name}!`);return true;}function hello(name) {
console.log(`Hello, ${name}!`);
return true;
}Long function parameters
Wrapped to multi-line.
function processOrder(customerId, productId, quantity, discountCode, shippingAddress) { /* ... */ }function processOrder(
customerId,
productId,
quantity,
discountCode,
shippingAddress,
) {
/* ... */
}Arrow function chain
Functional code formatted.
users.filter(u=>u.active).map(u=>({name:u.name,email:u.email})).sort((a,b)=>a.name.localeCompare(b.name))users
.filter((u) => u.active)
.map((u) => ({ name: u.name, email: u.email }))
.sort((a, b) => a.name.localeCompare(b.name));JSX component
React component with props.
const Button=({label,onClick,variant="primary"})=><button className={`btn btn-${variant}`} onClick={onClick}>{label}</button>const Button = ({ label, onClick, variant = "primary" }) => (
<button className={`btn btn-${variant}`} onClick={onClick}>
{label}
</button>
);TypeScript with types
Type annotations preserved.
interface User{id:number;name:string;email?:string;}function getUser(id:number):User|null{return db.users.find(u=>u.id===id)??null;}interface User {
id: number;
name: string;
email?: string;
}
function getUser(id: number): User | null {
return db.users.find((u) => u.id === id) ?? null;
}Object with trailing comma
ES5 trailing commas for cleaner diffs.
const config={apiUrl:"https://api.example.com",timeout:5000,retries:3}const config = {
apiUrl: "https://api.example.com",
timeout: 5000,
retries: 3,
};Technical details
Prettier-style formatting rules (applied by this tool):
Indentation: 2 spaces (default). Each nesting level adds 2 more spaces.
Line width: 80 characters. Lines are wrapped to fit within this width. Increases readability and side-by-side diff viewing.
Quote style:
- Double quotes for strings (default Prettier) or single quotes (configurable).
- Backticks only when interpolation is needed or when avoiding escape of the other quote.
Semicolons: Required at statement ends (default). Some teams prefer omitting semicolons — configurable.
Trailing commas:
- none — never trailing commas.
- es5 — trailing commas where ES5 allows (arrays, objects). Not in function parameters.
- all — trailing commas everywhere ES2017+ allows (including function parameters). Default in new Prettier — makes git diffs cleaner.
Bracket spacing:
- { foo: bar } vs {foo: bar} — space inside braces (default: yes).
Arrow function parens:
- (x) => x vs x => x — parens around single param (default: always parens for consistency).
Block indentation:
``js``
function example(
longParameter1,
longParameter2,
longParameter3,
) {
// body indented 2 spaces
}
Object/array formatting:
- Short objects on one line: { a: 1, b: 2 }.
- Long objects multi-line with trailing commas:
``js``
{
propertyOne: "value",
propertyTwo: "another",
propertyThree: "more",
}
JSX formatting:
- Short elements on one line.
- Long elements multi-line with props on separate lines.
- Children indented under parent.
Comments:
- // line comments preserved.
- /* block comments */ preserved.
- Leading/trailing blank lines around comments preserved.
String literals:
- Escape sequences preserved.
- Template literals ` preserved as-is.
Modern syntax supported:
- ES2015+ (arrow functions, classes, let/const, template literals, destructuring, spread/rest, modules).
- ES2017+ (async/await, object spread).
- ES2020+ (optional chaining, nullish coalescing, BigInt).
- ES2021+ (logical assignment, numeric separators).
- ES2022+ (class fields, top-level await).
- TypeScript (types, interfaces, generics, decorators).
- JSX/TSX (React syntax).
What is not changed:
- Logic or behavior.
- Variable and function names.
- Order of statements.
- Which exports/imports.
- Core algorithm.
What is changed:
- Whitespace.
- Indentation.
- Line breaks.
- Quote style (if different from target).
- Semicolons (if different from target).
- Trailing commas.
Comparison with linters:
- Formatter (Prettier, this tool): fixes cosmetic issues. No opinions about logic.
- Linter (ESLint, Stylelint): fixes logic issues, enforces conventions, catches bugs.
Use both: formatter for style, linter for correctness. ESLint and Prettier integrate well.
Common problems and solutions
⚠Different formatter than your project uses
Teams may use different configs (ESLint plugins, project .prettierrc). This formatter uses sensible defaults. Check your project rules and configure this tool to match.
⚠Formatter changes semantic meaning
Edge case: removing parentheses can change operator precedence. Modern formatters handle this correctly. If you see behavior change, file a bug.
⚠Comments move unexpectedly
Comments between non-standard positions (inside function parameters, etc.) may move to adjacent valid positions. Review if comments are critical.
⚠Template literals with complex escaping
Formatter may re-escape template literal contents. Usually benign but worth checking.
⚠Long regex literals
Regex expressions cannot be wrapped — kept on one line even if exceeding line width.
⚠JSX conditional rendering
Complex JSX conditionals may format differently than expected. Prettier has specific rules. Review after formatting.
⚠TypeScript generic constraints
Complex generics with multiple constraints format onto multiple lines. Usually correct but worth reviewing.
⚠Async/await formatting
Chained awaits stay on one line unless too long. For long chains, consider refactoring rather than relying on formatter.
JavaScript Formatter — comparisons and alternatives
This tool vs Prettier: Same rules. Prettier runs in editor/CI integration. This tool is for ad-hoc formatting.
JavaScript Formatter vs Minifier: Formatter expands for readability. Minifier compresses for production. Opposite operations, lossless roundtrip.
Prettier vs ESLint: Prettier formats style. ESLint catches semantic issues. Use both: Prettier for whitespace/quotes, ESLint for unused variables, potential bugs.
This tool vs editor integration: Editor integration auto-formats on save. This tool for quick checks, code from non-file sources (Slack, documentation, tickets).
JavaScript vs TypeScript formatting: Same rules apply. TypeScript adds type annotations. Formatter handles both.
JSX vs HTML formatting: Related but different. JSX uses JS rules; HTML has its own. This formatter handles JSX; use our HTML Formatter for HTML.
Frequently asked questions about the JavaScript Formatter
▶What does the formatter do?
Applies consistent indentation, spacing, quotes, and line breaks to JavaScript/TypeScript code. Based on Prettier rules — the industry-standard formatter used by React, Vue, Next.js, and most modern JS projects.
▶Is it the same as Prettier?
Compatible. Uses same rules. Prettier is the canonical tool; this is a browser-based alternative for quick formatting without installing anything.
▶What languages does it support?
JavaScript (ES5 through ES2024), TypeScript, JSX, TSX. Automatic detection or manual selection. Modern syntax features (async/await, optional chaining, private class fields) supported.
▶Is my code safe?
Yes. Formatting happens in your browser. Code never uploads. Safe for proprietary business logic, internal tools, client projects.
▶Should I use tabs or 2 spaces?
2 spaces is the modern default (Prettier, Airbnb, Google style guides). Match your project. Consistency matters more than which you pick.
▶Single or double quotes?
Double quotes is Prettier default. Single quotes common in many projects. Match your team. Tool supports both.
▶Semicolons or no semicolons?
With semicolons is safer (avoids ASI gotchas). Without is concise (Prettier supports noSemi mode). Both work in valid JS. Pick one, be consistent.
▶What are trailing commas?
Comma after the last element in arrays/objects. [1, 2, 3,] is valid. Benefits: cleaner git diffs (adding an element only changes one line). Prettier defaults to all (trailing commas everywhere allowed, including function parameters).
▶Can I format TypeScript?
Yes. Interfaces, types, generics, decorators all handled. Select TypeScript mode or let auto-detection handle it.
▶Does it format JSX/React?
Yes. JSX and TSX files formatted with Prettier JSX rules: props on separate lines for long elements, children indented, self-closing tags when appropriate.
Additional resources
- Prettier — Industry-standard code formatter.
- ESLint — JavaScript linter for catching issues.
- TypeScript — Official TypeScript site.
- Airbnb JavaScript Style Guide — Popular JS style conventions.
- Google JavaScript Style Guide — Google JS conventions.
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