fallow — Static analysis for AI-assisted JavaScript/TypeScript development

Fallow analyzes more than .js and .ts files. It extracts imports and exports from non-JavaScript file types automatically based on their extension, with no plugins or config needed.

Vue / Svelte
Astro
MDX
CSS / SCSS Modules
React Native

Fallow extracts the <script> block from Vue and Svelte single-file components and analyzes it like a standalone JS/TS module.What’s supported:

<script> and <script setup> blocks
lang="ts" and lang="tsx" attributes
<script src="./external.ts"> external script references
HTML comments () are filtered out before parsing

Example.vue

<script setup lang="ts">
import { ref } from 'vue'
import { formatDate } from '@/utils/date'

const count = ref(0)
</script>

<template>
  <div>{{ formatDate(new Date()) }}</div>
</template>

Fallow sees this file as importing ref from vue and formatDate from @/utils/date.

Svelte components export props implicitly. Fallow cannot distinguish between props and utility exports, which may cause false negatives for unused exports in .svelte files. See Limitations for details.

Astro components use a frontmatter block delimited by --- at the top of the file. Fallow extracts everything between the two --- delimiters and analyzes it as TypeScript.

Layout.astro

---
import Header from '../components/Header.astro'
import Footer from '../components/Footer.astro'
import type { Props } from './types'
---

<html>
  <body>
    <Header />
    <slot />
    <Footer />
  </body>
</html>

Fallow sees this file as importing Header, Footer, and the Props type.

MDX files can contain JavaScript import and export statements alongside Markdown content. Fallow extracts these statements and includes them in the module graph.

guide.mdx

import { CodeBlock } from '../components/CodeBlock'
import { Callout } from '../components/Callout'

export const meta = { title: 'Getting Started' }

# Getting Started

<CodeBlock language="bash">
  npm install fallow
</CodeBlock>

Fallow tracks the imports of CodeBlock and Callout, and the named export meta.

Fallow tracks CSS and SCSS module files (.module.css and .module.scss) by extracting class names as named exports. When a component imports styles from a CSS module, fallow knows which classes are defined.

Button.module.css

.root {
  display: flex;
}

.primary {
  background: blue;
}

.disabled {
  opacity: 0.5;
}

This file exports root, primary, and disabled as named exports.CSS features fallow tracks:

Feature	Description
`@import`	CSS import statements create edges in the module graph
`@use`	Sass `@use` rules are resolved as module imports
`@forward`	Sass `@forward` rules are treated as re-exports
`@apply` / `@tailwind`	Detected as Tailwind CSS dependency usage

When Tailwind is in your package.json, fallow recognizes @apply and @tailwind directives as evidence that the tailwindcss dependency is used, preventing false “unused dependency” reports.

React Native projects use platform-specific file extensions to provide different implementations per platform. Fallow understands these extensions and treats them as variants of the same module.Supported platform extensions:

Extension	Platform
`.web.ts` / `.web.tsx`	Web (react-native-web)
`.ios.ts` / `.ios.tsx`	iOS
`.android.ts` / `.android.tsx`	Android
`.native.ts` / `.native.tsx`	Native (iOS + Android)

src/
  Button.tsx          # Default implementation
  Button.web.tsx      # Web override
  Button.native.tsx   # Native override

When another file imports ./Button, fallow resolves it to all platform variants and considers each one reachable.

Dead code analysis

How fallow builds the module graph and detects unused code.

Built-in plugins

84 framework plugins for automatic entry point detection.

Getting Started

Analysis

Configuration

Frameworks

Integrations

Migration

Non-JS file types

See also

Dead code analysis

Built-in plugins

Getting Started

Analysis

Configuration

Frameworks

Integrations

Migration

​See also

Dead code analysis

Built-in plugins

See also