JavaScript Formatter Online

What this tool does

The tool splits your code into tokens the way a JavaScript engine does: names, numbers, strings, template literals with their ${…} parts, regular expressions, punctuators, comments and JSX. Whether a / starts a regex or divides, and whether a < starts a JSX tag, is decided from the token before it, as parsers do. Formatting then lays the tokens out again: one statement per line, braces on the same line as if, function and class, blocks and object literals indented, a space around operators and after commas, and at most one blank line where you had blank lines. Objects and arrays stay on one line when they are short and were written on one line; otherwise they get one item per line. Line breaks you wrote inside an expression, such as a long condition or a chain of .then() calls, are kept and indented. Only whitespace, line breaks and comments ever change: no semicolon is added or removed, quotes and numbers stay as written, and nothing is renamed. Minified mode removes comments, except /*! … */ and @license comments, and every space that cannot matter. It keeps a line break where JavaScript's automatic semicolon insertion depends on it, for example after return or before a line that starts with ++, and a space where two tokens would merge, as in a - -b. The check covers tokens and brackets, not the full grammar: a mistake such as const = 5 is formatted, not reported.

Example input and output

function greet(e){const t=e.trim();if(!t)throw new Error("name is required");return`Hello, ${t}!`}const users=["Ada","Linus"];for(const u of users)console.log(greet(u));

function greet(e) {
  const t = e.trim();
  if (!t) throw new Error("name is required");
  return `Hello, ${t}!`
}
const users = ["Ada", "Linus"];
for (const u of users) console.log(greet(u));

export function Price({ amount, currency = "EUR" }) {
const text = formatMoney(amount, currency);
    return (
  <p className="price">
      Total: <strong>{text}</strong>
        {amount > 100 && <span className="badge">Free shipping</span>}
   </p>
    );
}

export function Price({ amount, currency = "EUR" }) {
  const text = formatMoney(amount, currency);
  return (
    <p className="price">
      Total: <strong>{text}</strong>
      {amount > 100 && <span className="badge">Free shipping</span>}
    </p>
  );
}

/*! widget v2 | MIT */
// Count clicks
let count = 0
const button = document.querySelector("#save")
button.addEventListener("click", () => {
  count++
  render()
})

/*! widget v2 | MIT */let count=0
const button=document.querySelector("#save")
button.addEventListener("click",()=>{count++
render()})

Common errors and fixes

Unclosed string: the line ends before the closing "

A quote is missing. A string in single or double quotes cannot span lines, so everything after the opening quote is read as part of it up to the end of the line. Add the closing quote, or use a template literal (`…`) for text over several lines.

Unclosed {: it has no matching }

A } is missing, often at the end of a function or an if block. Everything after the { is still inside it, so the formatted output shows the rest of the file indented one level too deep: look for the point where the indentation stops matching what you meant, and add the } there.

Expected ) to close the ( on line 3, but found }

Brackets close in the reverse order they were opened. Here a call or condition that starts on line 3 is still open when a } arrives. Add the missing ), or remove the extra }. The message names the line of the opener, so you know which pair is wrong.

Unclosed ${ in a template literal: there is no } to end it

A substitution such as ${user.name has no closing }, so the backtick meant to end the template starts a new one instead. Add the }, then check that the template still ends with a backtick.

Unclosed regular expression: the line ends before the closing /

A / was read as the start of a regex. If you meant division, a value or a ) is probably missing just before it. If it is a regex, a / inside it must be written \/, unless it is inside a character class like [/].

Unexpected character “: curly quotes do not start or end strings in JavaScript

Code copied from a word processor, a slide or a chat app often has “ ” or ‘ ’ instead of straight quotes. Replace them with " or '. The same goes for invisible characters such as zero-width spaces, which the Invisible Character Finder shows.

Expected </span> to close <span> on line 2, but found </div>

In JSX every tag must be closed, and in the reverse order it was opened. Add the missing </span>, or write elements without children as <span />. A > or } in JSX text must be written {'>'} or {'}'}.

Common use cases

• Reading a minified bundle or library from a CDN, an npm package or a production build
• Tidying JavaScript copied from DevTools, Stack Overflow, a chat or an AI assistant
• Re-indenting a React component whose JSX was pasted with broken indentation
• Finding the unclosed string, bracket or template literal that breaks everything after it
• Minifying a snippet for a bookmarklet, an inline <script> or a CMS field
• Making two versions of a script comparable before diffing them

Privacy and security notes

• Your code is formatted by JavaScript in this browser tab. It is not sent to DevPrix or stored on a server.
• The code is never run: it is read as text and split into tokens, so formatting a script cannot execute it or make a network request.
• Share copies a link that carries your input after the # in the URL. Browsers do not send that part to servers, but anyone you give the link to can read it.

Frequently asked questions