Paste your broken JavaScript here and click "Fix JS!!" to repair itEnter Invalid JS

What is the JS Fixer?

You paste a snippet from a doc page or a chat thread and the parser blows up. A semicolon's missing where ASI didn't help. A brace got eaten. A string runs off the end of the line. This tool takes that broken JavaScript and gives you something the engine will actually accept.

JavaScript's grammar is defined by the TC39 ECMAScript spec, and that's what every browser and Node.js follows when parsing your code. The MDN JavaScript reference walks through the rules in plain language. Automatic Semicolon Insertion is part of that grammar — convenient most of the time, painful when a stray newline silently changes what your code means. This fixer targets the syntax-level breakage; if you also want a full reformat, run the output through Prettier after.

Everything runs through your browser to our backend and back. Use it as a first pass before you point <a href="https://eslint.org/" target="_blank" rel="noopener">ESLint</a> at the file — most rule violations are easier to read once the code at least parses.

How to Use the JS Fixer

Three steps. Each one uses the actual buttons and panels you see on this page.

Paste Broken JS or Load Sample

Drop your broken JavaScript into the left editor. Hit Sample JS if you want to see the kind of input the fixer chews on. The classic mess looks something like this — missing semicolons, a missing comma in an object literal, an unbalanced brace, a value that should've been a string but got typed without quotes:

function processOrder(customer) {
  const order = { id: "ORD-9001" customer: customer, status: pending }
  return order

The fixer handles missing semicolons, mismatched `{`/`}`, `[`/`]`, and `(`/`)`, missing commas in object and array literals, unquoted string values, unterminated strings, and stray operator combinations.

Click Fix JS!!

Hit the green Fix JS!! button. The code goes to the backend, gets repaired, comes back parseable. There's a loading indicator while that's happening — usually a second or two.

Review the Output

The right panel shows the fixed code. The semantics stay as close as possible to your input — only the syntax is repaired. Copy the output, drop it back into your editor, and run your formatter or linter on it.

When You'd Actually Use This

Recovering Pasted Snippets

Code that comes off a Slack thread, a StackOverflow answer, or a PDF often loses quotes, line continuations, or whole punctuation marks in transit. Run it through here before you start hand-editing.

Debugging Extracted Minified Code

When you're reading a stack trace from a production bundle and you grab a fragment to inspect, getting it to parse is half the battle. Fix the syntax first, then beautify, then dig in.

ASI Surprises

Code that relied on automatic semicolon insertion can break in subtle ways — `return` followed by a newline silently returns `undefined`, for example. The fixer adds explicit semicolons where the parser wants them so the next reader sees what's actually happening.

Cleaning Up AI-Generated Stubs

Snippets generated by an LLM occasionally drop a brace or skip a comma. Fix the syntax here before piping the result into Babel or your bundler.

Common Questions

Is my code stored anywhere?

It's sent to our backend so the AI model can fix it, then we hand the result back. We don't log the code, we don't train on it, and we don't use it for anything except repairing this one request.

What kinds of errors does it fix?

Syntax-level stuff: missing semicolons, mismatched braces / brackets / parens, missing commas in object and array literals, unquoted values where a string was expected, unterminated string and template literals, malformed operator combinations. Logical bugs (wrong condition, off-by-one) are out of scope — the fixer doesn't reason about your business logic.

Will it change the meaning of my code?

It tries hard not to. The goal is to keep your semantics intact and only repair the grammar. There are edge cases where some interpretation is needed (an unquoted token sitting where a string clearly belongs, for instance) — in those cases the fixer picks the most likely intent. Always eyeball the output.

Does it support TypeScript?

TypeScript-specific syntax — type annotations, generics, decorators — is out of scope. The JS subset of TS (classes, async/await, template literals, modern array methods) parses cleanly. If you want a proper TS upgrade, see our JS to TypeScript tool.

Can I use this on production code?

It's a syntax-repair tool, not a substitute for a linter or type checker. Treat the output as a starting point — pipe it into ESLint and your test suite before you ship it.

Is there code it just can't fix?

Sometimes. If the input is too fragmentary or the original intent is genuinely ambiguous (multiple plausible repairs), the fixer will pick one — but the result may be syntactically valid yet semantically wrong. Always review the output, especially for inputs shorter than a few lines.

Other JavaScript Tools You Might Need

Fixing the syntax is just step one. Here are the other JavaScript tools on the site: