TypeScript Sourcemaps FAQ & Answers

Production builds are minified and mangled, converting readable TypeScript to compressed JavaScript. Variable names become single letters, function names shortened, whitespace removed. Without sourcemaps, error stack traces show minified code making debugging impossible. Example: 'Cannot read property of undefined at e.t (bundle.js:1:34567)' - no context. Solution: Generate sourcemaps with sourceMap: true in tsconfig.json. Sourcemaps create .map files that browser DevTools use to show original TypeScript code and line numbers during debugging.

Set sourceMap: true in tsconfig.json compilerOptions. Pattern: { 'compilerOptions': { 'sourceMap': true, 'inlineSources': true, 'sourceRoot': '/' }}. This generates .map files alongside .js files. inlineSources embeds original TypeScript in map file (larger but simpler deployment). sourceRoot tells debugger where to find sources. For production: Keep sourceMap: true but don't deploy .map files publicly (upload to Sentry instead). Webpack: set devtool: 'source-map' in production config. Verify: Check if .js.map files generated in dist folder.

No, don't expose sourcemaps publicly - security risk. They reveal: original code structure, variable names, business logic, API endpoints, algorithm implementations. Better approaches: (1) Upload to error tracking (Sentry/Datadog) for private access, (2) Serve from authenticated endpoint, (3) Don't deploy at all (use Node.js --enable-source-maps for server-side only). Pattern: Build with sourcemaps, upload to Sentry, delete .map files before deployment. Sentry uses maps to de-obfuscate errors without exposing code publicly. Only expose if: open source project, no sensitive logic.

Node.js 12.12+ supports --enable-source-maps flag. Pattern: node --enable-source-maps dist/app.js. This automatically loads .map files and shows original TypeScript in error stack traces. No browser needed. For PM2: pm2 start app.js --node-args='--enable-source-maps'. For Docker: CMD ['node', '--enable-source-maps', 'dist/app.js']. Verify working: Throw error, check stack trace shows .ts files not .js. Performance impact: negligible (<1%). Always enable in production for better error debugging. Alternative: Use source-map-support npm package for Node <12.12.

Common causes: (1) .map files not deployed with .js files, (2) sourceRoot incorrect in tsconfig, (3) Browser cache showing old version, (4) .map files blocked by CSP headers, (5) Webpack devtool: 'eval' in production (wrong setting). Debug: Open DevTools Network tab, check if .map files loading (should see requests for bundle.js.map). Check browser console for sourcemap errors. Verify: In Sources tab, should see webpack:// or ts:// folders with original files. Fix: Deploy .map files, set sourceRoot: '/', hard refresh browser (Ctrl+Shift+R).

Use devtool: 'source-map' for production. This generates separate .map files with high quality mappings. NOT: 'eval' (no sourcemaps, dev only), 'eval-source-map' (slow, dev only), 'cheap-source-map' (line-only, inaccurate). Pattern: const config = { mode: 'production', devtool: 'source-map', output: { filename: '[name].[contenthash].js' }}. Alternative: 'hidden-source-map' generates maps but doesn't reference them in bundle (for Sentry upload only). Balance: 'source-map' = best quality + larger files, 'nosources-source-map' = smaller files + less debug info. Choose based on security needs.

Install @sentry/webpack-plugin, configure in webpack. Pattern: const SentryWebpackPlugin = require('@sentry/webpack-plugin'); plugins: [new SentryWebpackPlugin({ authToken: process.env.SENTRY_AUTH_TOKEN, org: 'my-org', project: 'my-project', include: './dist', ignore: ['node_modules', 'webpack.config.js'], release: process.env.RELEASE_VERSION })]. This uploads maps during build. Sentry stores privately, uses to de-obfuscate errors. Delete .map files from deployment after upload. For manual upload: sentry-cli releases files upload-sourcemaps ./dist. Verify: Check Sentry release artifacts, errors should show original TypeScript.

Production builds are minified and mangled, converting readable TypeScript to compressed JavaScript. Variable names become single letters, function names shortened, whitespace removed. Without sourcemaps, error stack traces show minified code making debugging impossible. Example: 'Cannot read property of undefined at e.t (bundle.js:1:34567)' - no context. Solution: Generate sourcemaps with sourceMap: true in tsconfig.json. Sourcemaps create .map files that browser DevTools use to show original TypeScript code and line numbers during debugging.

Set sourceMap: true in tsconfig.json compilerOptions. Pattern: { 'compilerOptions': { 'sourceMap': true, 'inlineSources': true, 'sourceRoot': '/' }}. This generates .map files alongside .js files. inlineSources embeds original TypeScript in map file (larger but simpler deployment). sourceRoot tells debugger where to find sources. For production: Keep sourceMap: true but don't deploy .map files publicly (upload to Sentry instead). Webpack: set devtool: 'source-map' in production config. Verify: Check if .js.map files generated in dist folder.

No, don't expose sourcemaps publicly - security risk. They reveal: original code structure, variable names, business logic, API endpoints, algorithm implementations. Better approaches: (1) Upload to error tracking (Sentry/Datadog) for private access, (2) Serve from authenticated endpoint, (3) Don't deploy at all (use Node.js --enable-source-maps for server-side only). Pattern: Build with sourcemaps, upload to Sentry, delete .map files before deployment. Sentry uses maps to de-obfuscate errors without exposing code publicly. Only expose if: open source project, no sensitive logic.

Node.js 12.12+ supports --enable-source-maps flag. Pattern: node --enable-source-maps dist/app.js. This automatically loads .map files and shows original TypeScript in error stack traces. No browser needed. For PM2: pm2 start app.js --node-args='--enable-source-maps'. For Docker: CMD ['node', '--enable-source-maps', 'dist/app.js']. Verify working: Throw error, check stack trace shows .ts files not .js. Performance impact: negligible (<1%). Always enable in production for better error debugging. Alternative: Use source-map-support npm package for Node <12.12.

Common causes: (1) .map files not deployed with .js files, (2) sourceRoot incorrect in tsconfig, (3) Browser cache showing old version, (4) .map files blocked by CSP headers, (5) Webpack devtool: 'eval' in production (wrong setting). Debug: Open DevTools Network tab, check if .map files loading (should see requests for bundle.js.map). Check browser console for sourcemap errors. Verify: In Sources tab, should see webpack:// or ts:// folders with original files. Fix: Deploy .map files, set sourceRoot: '/', hard refresh browser (Ctrl+Shift+R).

Use devtool: 'source-map' for production. This generates separate .map files with high quality mappings. NOT: 'eval' (no sourcemaps, dev only), 'eval-source-map' (slow, dev only), 'cheap-source-map' (line-only, inaccurate). Pattern: const config = { mode: 'production', devtool: 'source-map', output: { filename: '[name].[contenthash].js' }}. Alternative: 'hidden-source-map' generates maps but doesn't reference them in bundle (for Sentry upload only). Balance: 'source-map' = best quality + larger files, 'nosources-source-map' = smaller files + less debug info. Choose based on security needs.

Install @sentry/webpack-plugin, configure in webpack. Pattern: const SentryWebpackPlugin = require('@sentry/webpack-plugin'); plugins: [new SentryWebpackPlugin({ authToken: process.env.SENTRY_AUTH_TOKEN, org: 'my-org', project: 'my-project', include: './dist', ignore: ['node_modules', 'webpack.config.js'], release: process.env.RELEASE_VERSION })]. This uploads maps during build. Sentry stores privately, uses to de-obfuscate errors. Delete .map files from deployment after upload. For manual upload: sentry-cli releases files upload-sourcemaps ./dist. Verify: Check Sentry release artifacts, errors should show original TypeScript.