TSFIX

A post-compilation tool that fixes TypeScript's critical ESM compatibility failures. Properly adds .js extensions, resolves path aliases, and handles index.js imports where tsc consistently falls short, even in the latest versions.

Complete Solution for All TypeScript Issues

✅ Fixes Extension Problems: Adds required .js extensions to imports
✅ Handles Directory Imports: Properly resolves to index.js files
✅ Transforms Path Aliases: Converts tsconfig aliases to valid relative paths
✅ Fixes Declaration Files: Properly handles .d.ts files (unlike TypeScript itself)
✅ Zero Configuration: Works out-of-the-box with any TypeScript setup
✅ Universal Compatibility: Works with all TypeScript versions and config setups
✅ High Performance: Offers both fast regex mode and accurate AST mode

Zero Hassle Setup

npm install --save-dev @2bad/tsfix

Then add postbuild script to your package.json:

{
  "scripts": {
    "build": "tsc",
    "postbuild": "tsfix"
  }
}

That's it. TSFIX finds your TypeScript output and fixes all import issues automatically.

Real World Examples

Converting Regular Imports

// Before TypeScript Compilation
import { helper } from './utils/helper.ts'

// After TypeScript Compilation (BROKEN)
import { helper } from './utils/helper.ts'

// After TSFIX (FIXED)
import { helper } from './utils/helper.js' // Works in ESM!

Fixing Path Alias Imports

// tsconfig.json
{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "@/*": ["src/*"]
    }
  }
}

// Before TypeScript Compilation
import { Button } from '@/components/Button'

// After TypeScript Compilation (BROKEN)
import { Button } from '@/components/Button'

// After TSFIX (FIXED)
import { Button } from './src/components/Button.js' // Correctly resolved!

Resolving Directory Imports

// Before TypeScript Compilation
import { config } from './config'

// After TypeScript Compilation (BROKEN)
import { config } from './config'

// After TSFIX (FIXED)
import { config } from './config/index.js' // Properly resolved!

Advanced Usage

# Use AST-based extraction (more accurate but slower)
npx @2bad/tsfix --mode ast

# Custom file matching pattern
npx @2bad/tsfix --pattern "**/*.js"

Debugging

# Enable all debug logging
DEBUG=* tsfix

# Only enable specific components
DEBUG=tsfix:main,tsfix:extractor tsfix

# Show only fixer operations
DEBUG=tsfix:fixer tsfix

Why TSFIX exists

Major TypeScript Issues (Still Unresolved)

#16577: Provide a way to add the '.js' file extension to the end of module specifiers (2017)
#28288: Feature: disable extensionless imports (2018)
#40878: Compiled JavaScript import is missing file extension (2020)
#42151: TypeScript cannot emit valid ES modules due to file extension issue (2020)
#50501: TypeScript is not an ECMAScript superset post-ES2015 (2022)
#61037: rewriteRelativeImportExtensions doesn't rewrite extensions in emitted declaration files (2025)
#61213: Allow allowImportingTsExtensions: without either '--noEmit' or '--emitDeclarationOnly' (2025)

Previously Addressed (Partially)

#49083: "module": "node16" should support extension rewriting (Partially addressed via #59767)

Performance Options

TSFIX offers two extraction engines:

Regex mode (default): Fast pattern-based extraction (5x faster than AST mode)
AST mode: Precise syntax tree-based extraction for complex codebases

Contributing

Contributions welcome! Open issues for bugs/features or submit PRs with improvements.