Indented JavaScript with clearer line breaks. The example should still calculate 27 when run in the playground.
CHECK & OPTIMIZE · FREE JAVASCRIPT TOOL
JavaScript Code Formatter & Beautifier
Format untidy JavaScript into readable, consistently indented source and download the result.
Free to useNo sign-upRuns in your browser
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A WORKED TASK
Read a cramped function before changing it
The sample adds the values 4, 8 and 15 using reduce. Format it to separate the function body, callback and final call. Compare the formatted output against the original, then download the new source. Consistent layout makes the code easier to review, but it is not a behavioral change.
This uses js-beautify. It is not a TypeScript compiler, ESLint rule engine or automatic security repair. Readable source can still contain faulty or harmful logic.
What to check
- Keep strings and template literals intact when reviewing the result.
- Review the output before replacing a project file, especially for unusual syntax.
- Use the syntax checker for incomplete code; layout changes cannot infer a missing expression.
TESTED & REVIEWED
Know what this tool does—and where to double-check
- Reviewed by
- HTML Online Viewer project
- Last reviewed
- Processing
- Ordinary processing happens in this browser tab; the tool does not intentionally upload your source.
- Important limitation
- JavaScript checks and transformations cannot prove that application logic is correct. Test the result in its real project before publishing.
PRACTICAL EXAMPLE
Start with a small JS Formatter example
The built-in sample makes the accepted input visible before you use your own project data.Example input
Loaded in the workspace
const total=(values)=>{return values.reduce((sum,value)=>sum+value,0)};console.log(total([4,8,15]));Run the sample first, then change one value at a time so each result remains easy to explain.
What this example demonstrates
Format untidy JavaScript into readable, consistently indented source and download the result.
Keep the original file, review the generated result and test production code in its real application before publishing.
COMMON QUESTIONS
JS Formatter FAQ
Is JS Formatter free?
Yes. It is free to use and requires no account.
Does JS Formatter upload my source?
No. Ordinary processing happens locally in the current browser. The JavaScript runner uses a short-lived isolated browser worker.
Can I import and export a file with JS Formatter?
Yes. Import a relevant JavaScript, JSON or text file, then save the input or processed result.