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JavaScript Formatter

Turn compressed or unformatted JavaScript into clean, indented source code. Useful for reviewing bundled output, snippets, and legacy scripts.

Formatted JavaScript

What is a JavaScript formatter?

A JavaScript formatter (also called a JS beautifier) takes source code and rewrites it with consistent indentation, brace placement, and line breaks so the control flow is easy to follow. JavaScript powers front-end applications, Node.js services, serverless functions, browser extensions, and embedded scripts. Developers constantly encounter compressed code — from npm bundles, bookmarklets, legacy scripts, and copied Stack Overflow snippets — that is painful to read and dangerous to edit without seeing the structure.

This tool expands that code instantly. Paste any JavaScript snippet, choose 2-space, 4-space, or tab indentation, and get readable output. Copy the result to your IDE, download a .js file, or continue reviewing in the output panel. Processing uses the js-beautify library and runs entirely in your browser.

How to use the JavaScript formatter

  1. Paste your code into the input panel. Click Load sample to try a function with destructuring and an array iteration.
  2. Choose indentation from the dropdown.
  3. Click Format to beautify the code.
  4. Review the output — blocks, callbacks, and object literals are indented to reflect nesting depth.
  5. Copy or download the formatted JavaScript.

Example

Before: minified function

function sum(arr){return arr.reduce((a,b)=>a+b,0);}const data=[1,2,3,4];console.log(sum(data));

After: formatted

function sum(arr) {
  return arr.reduce((a, b) => a + b, 0);
}
const data = [1, 2, 3, 4];
console.log(sum(data));

The arrow function callback and return statement are immediately visible. That clarity matters when auditing third-party scripts or debugging minified error stack traces.

Why formatting JavaScript matters

Readable code reduces defect rates. When braces align and indentation reflects scope, off-by-one logic errors and missing return statements stand out. Security reviews of third-party snippets require understanding control flow — a formatted script reveals eval calls, unexpected network requests, and obfuscated patterns faster than a single-line blob.

Education benefits too. Learners parsing callbacks, closures, and async patterns need visual structure. A formatter turns a dense one-liner into a teaching diagram without changing behavior.

Common scenarios

  • Bundle inspection — Expand a suspicious function extracted from a minified vendor file.
  • Legacy maintenance — Beautify old jQuery or Prototype scripts before refactoring.
  • Code review prep — Normalize indentation on pasted snippets before adding them to a pull request.
  • Documentation — Publish readable examples in blog posts and API guides.

Related tools

Frequently asked questions

Does formatting JavaScript change how it runs?
No. Formatting only adjusts whitespace, line breaks, and indentation. It does not rename variables, reorder statements, or alter string literals (except within safe re-indentation). The code produces the same behavior before and after formatting.
Can I format minified or bundled JavaScript?
Yes, for reasonably sized snippets. Webpack, Rollup, and Terser output can be pasted and expanded for inspection. Extremely large bundles may hit the 512,000-character input limit; extract the relevant function or module instead.
Does the formatter fix syntax errors?
No. It beautifies syntactically valid JavaScript using js-beautify. Severely broken code may fail to format or produce unexpected output. Fix syntax errors first, then format.
Is my code sent to a server?
No. Formatting runs entirely in your browser. Proprietary algorithms, API keys in strings, and internal business logic are never uploaded.
Does it support TypeScript or JSX?
The formatter handles JavaScript and many JSX patterns. TypeScript-specific syntax (type annotations, interfaces) may not format perfectly because it targets JavaScript. For TSX-heavy files, consider a dedicated IDE formatter for best results.
When should I use a formatter vs. a linter?
A formatter adjusts whitespace for readability. A linter (ESLint) enforces code quality rules, catches bugs, and may also fix style. Use this tool for quick beautification of snippets; use a linter in your project for ongoing enforcement.

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