Beautify JavaScript — Format and Pretty-Print JS Code

How JavaScript Beautification Works

JavaScript beautification (also called pretty-printing) is the reverse of minification. It takes compact, hard-to-read code and restores human-friendly formatting with proper indentation, line breaks, and spacing.

Before and After

// Minified input
function greet(e){if(!e)return"Hello, stranger!";const t=e.charAt(0).toUpperCase()+e.slice(1);return"Hello, "+t+"!"}

After beautification:

function greet(e) {
  if (!e) return "Hello, stranger!";
  const t = e.charAt(0).toUpperCase() + e.slice(1);
  return "Hello, " + t + "!";
}

What Beautification Cannot Restore

Beautification adds whitespace and structure, but it cannot undo:

• Variable name mangling — e and t remain shortened because the original names are lost during minification.
• Removed comments — Documentation and inline explanations are permanently gone.
• Simplified expressions — Constant-folded values or collapsed statements stay in their optimized form.

For full reverse-engineering of minified code, you need a source map (if available) or manual analysis.

AST-Based vs. Regex-Based Formatting

• AST-based formatters (Prettier, js-beautify) parse the code into an Abstract Syntax Tree, then re-print it according to formatting rules. This produces correct, consistent output even for complex syntax.
• Regex-based formatters apply pattern matching to insert line breaks and indentation. They are faster but can misformat edge cases like template literals, regex patterns, or nested ternaries.

Formatting Options

Most beautifiers let you configure:

• Indent style — Tabs vs. spaces (2 or 4 spaces being most common)
• Brace style — Same-line (collapse) or next-line (expand)
• Semicolons — Insert or omit trailing semicolons
• Quote style — Single vs. double quotes
• Max line width — Wrap long lines at a specified column

When to Beautify

• Debugging production issues when source maps are unavailable
• Reviewing third-party library code
• Reformatting inconsistent code before applying a linter
• Making copy-pasted code snippets readable