🧩 formpipe

A composable, lightweight, middleware-style input validation library for JavaScript/TypeScript.
Built for React, works anywhere.

✨ Features

• ✅ Middleware-style API for sequential validation
• ✅ Built-in validators (e.g., email, trimmed_not_empty, not_empty)
• ✅ Supports custom validators with typed error codes
• ✅ Framework-agnostic: works in React, Vue, Svelte, Vanilla JS
• ✅ TypeScript-first with full IntelliSense

📦 Installation

npm install formpipe
# or
yarn add formpipe

🚀 quick start

formpipe makes validation composable and developer-friendly using a middleware pipeline.

🧱 Setup

/* SETUP */
import { createValidationMiddleware, coreValidators } from "formpipe";

const middleware = createValidationMiddleware(coreValidators);

✅ Use

/* USAGE */
const { result, value, error, errorCode } = middleware({
  steps: ["non_empty", "email"],
  value: "  [email protected]  ",
});

if (result === "accepted") {
  console.log(value); // '[email protected]'
} else {
  console.error(error); // e.g., "Invalid email"
}

🛠 Extensible - Custom Validators

You can define your own validator logic and plug it into the middleware.

🧾 Define

/* DEFINE */
import { MiddlewareOutput, Validator } from "formpipe";

const usernameValidator: Validator = (value: string): MiddlewareOutput => {
  if (!value) {
    return {
      result: "not_accepted",
      value,
      error: "Username required",
      errorCode: "USERNAME_REQUIRED",
    };
  }
  if (value.length < 3) {
    return {
      result: "not_accepted",
      value,
      error: "Too short",
      errorCode: "USERNAME_TOO_SHORT",
    };
  }
  return { result: "accepted", value, errorCode: "NONE" };
};

const customValidators = {
  username: usernameValidator,
};

🧱 Setup

/* SETUP */
import {
  createValidationMiddleware,
  combineValidators,
  coreValidators,
} from "formpipe";

const allValidators = combineValidators(coreValidators, customValidators);
const middleware = createValidationMiddleware(allValidators);

✅ Use

/* USAGE */
const { result, value, error, errorCode } = middleware({
  steps: ["username"],
  value: "   user   ",
});

if (result === "accepted") {
  console.log(value); // '[email protected]'
} else {
  console.error(errorCode); // e.g., "USERNAME_REQUIRED" or "USERNAME_TOO_SHORT"
}

📚 API Reference

createValidationMiddleware(validators)

Creates a validation pipeline from a map of named validators.

export type ValidationResult = "accepted" | "not_accepted";

export interface MiddlewareOutput {
  result: ValidationResult;
  value: string;
  error?: string;
  errorCode: string;
}

export type Validator = (value: string) => MiddlewareOutput;

middleware({ steps, value}: {
    value: string;
    steps: (keyof T)[];  // where T = CoreValidators & typeof customValidators
})

Executes validators sequentially. If any validator fails, it short-circuits and returns an error.

📄 License

MIT License © 2025 Tarun Jakkula