xml-formatter

xml-formatter converts XML strings into human-readable, indented output, correctly respecting the xml:space="preserve" attribute so whitespace-sensitive content (like inline text with mixed markup) isn’t mangled during formatting — something naive regex-based XML prettifiers commonly get wrong. It can also run in reverse to minify already-formatted XML back down to a compact string.

The library works in both Node.js and browsers (via a browserified build), and supports configurable indentation, per-path node filtering/ignoring, and content-collapsing options, making it useful for XML config viewers, diff tools, or any pipeline that needs to display or normalize XML for humans.

What You Get

• A single xmlFormat() function to pretty-print XML with configurable indentation
• Correct handling of xml:space="preserve" so mixed text/element content keeps its intended whitespace
• A minify mode (xmlFormat.minify()) to collapse formatted XML back to a compact string
• Node filtering (filter) and path-based ignoring (ignoredPaths) to skip or preserve specific elements during formatting
• Works in Node.js and in browsers via a pre-built browserified bundle

Common Use Cases

• Pretty-printing XML API responses or config files for display in developer tools or logs
• Normalizing XML before diffing two documents so formatting differences don’t create false positives
• Minifying human-edited XML config files before storage or transmission to reduce payload size
• Building XML viewers or editors that need readable, correctly indented output while preserving significant whitespace in content

Under The Hood

Architecture The entire implementation lives in a single src/index.ts (~290 lines) that first parses the input XML into a lightweight node tree (leveraging a bundled parser), then walks that tree recursively to emit indented output, tracking an xml:space context flag as it descends so preserved-whitespace subtrees are emitted verbatim rather than re-indented. Tech Stack Written in TypeScript with zero runtime dependencies beyond its internal parser, compiled to three separate targets — CommonJS, ESM, and a Browserify bundle — via distinct tsc/browserify build scripts, reflecting an explicit goal of working identically in Node.js, ESM bundlers, and directly in browsers via a <script> tag. Code Quality Tests in test/ run via mocha with ts-node, covering both a Node test suite and a dedicated browser test runner (test/browser/run-browser-tests.ts) to verify the browserified build behaves identically to the Node build; the project uses renovate.json for automated dependency updates and ESLint for linting. API Design The primary API is a single function call — xmlFormat(xmlString, options) — with an options object covering indentation, filter, ignoredPaths, and collapseContent, keeping the common case (just prettify this XML) to one line while still exposing enough hooks for selective node handling.