GitHub - MarceloDelgadoDev/asp-classic-emulator: Run ASP Classic on macOS, Linux and BSD. Drop npx asp-emulator into any project folder and get a high-fidelity VBScript HTTP server — no Windows, no IIS, no VM. Full ASP object model, SQLite/MySQL/PostgreSQL support, and a hand-written Chevrotain parser.

Run ASP Classic on macOS, Linux and BSD.No Windows. No IIS. No VM.npx asp-classic-emulator

What is this? ASP Classic never died — it just got stranded on Windows. Millions of lines of VBScript are still running in production, and maintaining them means either keeping a Windows Server around or setting up a VM every time someone needs to touch the code. asp-classic-emulator fixes that. Drop it into any folder with .asp files, run one command, and get a fully working HTTP server that interprets VBScript with high fidelity to the original IIS behavior — on any POSIX system. your-project/ ├── index.asp ├── login.asp ├── includes/ │ └── conn.asp └── global.asa

cd your-project npx asp-classic-emulator # → Serving on http://localhost:3000

Features

Zero config — works out of the box with a single command High-fidelity VBScript — hand-written Chevrotain parser, proper Variant type system, implicit coercion with terminal warnings Full ASP object model — Response, Request, Session, Application, Server Database support — SQLite (built-in, zero config), MySQL/MariaDB, PostgreSQL ADO emulation — ADODB.Connection, ADODB.Recordset with classic connection strings CreateObject support — ADODB.*, Scripting.FileSystemObject, MSXML2.DOMDocument #include — file and virtual, resolved at runtime with cache and circular reference detection global.asa — Application_OnStart, Session_OnStart events Two error modes — modern stack trace in dev, classic IIS-style error page in prod Static file serving — CSS, JS, images served automatically alongside .asp files Watch mode — auto-reloads on file changes in development --strict mode — turns implicit type coercions into hard errors Multiple distribution options — npx, global install, Node.js API, Docker

Quick start Requirements

Node.js ≥ 18 macOS, Linux, or BSD

Run without installing npx asp-classic-emulator Install globally npm install -g asp-classic-emulator asp-classic-emulator Use as a Node.js library npm install asp-classic-emulator import { createServer } from 'asp-classic-emulator'

const server = createServer({ root: './www', port: 3000, mode: 'dev', })

await server.start() Docker docker run -p 3000:3000 -v $(pwd)/www:/app/www ghcr.io/asp-classic-emulator/asp-classic-emulator

Usage asp-classic-emulator [options]

Options: --port Port to listen on [default: 3000] --root Root folder with .asp files [default: .] --mode dev or prod [default: dev] --strict Throw on implicit type coercions [default: false] --watch Reload on file changes [default: true in dev] --timeout Script execution timeout (seconds) [default: 90] --log-level silent | error | warn | info | debug [default: info] --config Path to config file [default: asp-classic-emulator.config.json] --help Show help

Config file Create asp-classic-emulator.config.json in your project root. CLI flags override config values. { "port": 3000, "root": "./www", "mode": "dev", "strict": false, "watch": true, "timeout": 90, "session": { "timeout": 20 }, "databases": { "default": "Provider=SQLite;Data Source=./db.sqlite" }, "virtualDirectories": { "/includes": "./shared/includes" } }

VBScript support Phase 1 (current)

Construct Status

Dim, ReDim, Set ✅

Variable assignment ✅

If / ElseIf / Else / End If ✅

For / Next ✅

For Each

/ Next ✅

While / Wend ✅

Do / Loop ✅

Sub / End Sub ✅

Function / End Function ✅

Fixed and dynamic arrays ✅

Expressions (arithmetic, logical, comparison, string) ✅

Exit For, Exit Do, Exit Sub, Exit Function ✅

Phase 2 (planned)

Construct Status

Select Case 🔜

On Error Resume Next / Err object 🔜

With / End With 🔜

Class / End Class 🔜

Execute / ExecuteGlobal 🔜

Full VBScript built-in functions 🔜

Type system VBScript's Variant type is fully emulated. Every variable can hold any subtype and changes at runtime — just like the original. Dim x x = 42 ' Long x = "hello" ' String x = True ' Boolean x = Null ' Null (contagious in expressions) x = Empty ' Empty (zero in numeric context) Implicit coercion By default, implicit coercions work exactly as in IIS, and a warning is printed to the terminal: [WARN] Implicit coercion in /dashboard.asp:12 — String "42" → Number Use CInt() or CDbl() for explicit conversion. Run with --strict to throw instead.

Use --strict to turn all implicit coercions into runtime errors: asp-classic-emulator --strict

Database support Connection strings use classic ADO syntax — no changes needed to existing code. Dim conn Set conn = Server.CreateObject("ADODB.Connection")

' SQLite conn.Open "Provider=SQLite;Data Source=" & Server.MapPath("./db.sqlite")

' MySQL conn.Open "Provider=MySQL;Data Source=localhost;Database=mydb;User Id=root;Password=secret"

' PostgreSQL conn.Open "Provider=PostgreSQL;Data Source=localhost;Database=mydb;User Id=postgres;Password=secret"

Dim rs Set rs = conn.Execute("SELECT * FROM users WHERE active = 1")

Do While Not rs.EOF Response.Write rs("name") & "<br>" rs.

MoveNext Loop

rs.Close conn.Close

Error pages Development mode Clear, modern error page with file name, line number, column, source excerpt, and full interpreter stack trace. Production mode (--mode=prod) Classic IIS-style error page — exactly what end users would see on a real Windows server: Microsoft VBScript runtime error '800a000d' Type mismatch /pagina.asp, line 42

Supported file types

Extension Behavior

.asp Interpreted — <% %> blocks executed

.asa global.asa events (Application_OnStart, etc.)

.inc Interpreted when included via #include

.html, .htm Interpreted (supports embedded ASP blocks)

.css, .js, .png, .jpg, .gif, .svg, .ico Served as static files

Other Served as application/octet-stream

Terminal output ┌─────────────────────────────────────────┐ │ ASP Emulator v0.1.0 │ │ Serving: ./www │ │ http://localhost:3000 │ │ Mode: development · Watch: on │ └─────────────────────────────────────────┘

GET /index.asp 200 11ms GET /css/style.css 200 2ms POST /login.asp 302 6ms GET /dashboard.asp 200 28ms [WARN] implicit coercion in /dashboard.asp:42 — String → Number GET /report.asp 500 4ms [ERROR] /report.asp:17 — Object required: 'rs'

Architecture HTTP Request │ ▼ HTTP Server (node:http) │ ▼ Request Parser ── QueryString, Form, Cookies, Headers │ ▼ ASP Pre-processor ── resolve #include, split

HTML / <% %> │ ▼ Lexer (Chevrotain) ── text → typed token stream │ ▼ Parser (Chevrotain) ── tokens → AST with line/column info │ ▼ Interpreter ── walks AST, injects ASP objects, executes VBScript │ ▼ HTTP Response ── flush HTML buffer to client

Why a hand-written parser? No usable VBScript parser exists in the Node.js ecosystem. The few packages that exist are abandoned, incomplete, or cover less than 60% of the grammar. Chevrotain was chosen because:

TypeScript native — no separate grammar file, no code generation step Incrementally extensible — adding Select Case or With is a new method, nothing existing breaks Built-in error recovery — precise line and column in every error message Production-grade — used by SAP, MongoDB, and others

Contributing Contributions are welcome, especially:

VBScript built-in functions (Split, Join, Replace, Mid, DateAdd, etc.) Additional CreateObject implementations Real-world ASP fixture files for the test suite (anonymized is fine) Bug reports with .asp snippets that don't behave like IIS

git clone https://github.com/your-org/asp-classic-emulator cd asp-classic-emulator npm install npm run dev # starts the emulator pointing to ./examples/hello-world npm test

License MIT — see LICENSE for details.

Built for the developers keeping legacy systems alive.