frmz

A schema-aware reactive FormData builder with Zod validation and full Blob/File support. Manage form state, validate data, and generate submission-ready FormData with a reactive proxy.

Features

• ✅ Automatic Schema Inference: Derive Zod schemas from your data structures
• ✅ Manual Schema Validation: Use custom Zod schemas for precise control
• ✅ Reactive Data Proxy: Live updates with deep object reactivity
• ✅ Blob & File Support: Perfect for file uploads and image handling
• ✅ TypeScript First: Full type safety and intelligent inference
• ✅ FormData Generation: Create fetch-ready FormData objects automatically

Installation

Copy the src/index.ts into your project if you don't want to add additional dependencies to your project or

npm install frmz zod

pnpm add frmz zod

Note: Zod is a peer dependency and must be installed separately.

Basic Usage

import { frmz } from "frmz";

// Create a form manager with automatic schema inference
const { data, getFormData } = frmz({
  user: {
    name: "Alice",
    email: "alice@example.com",
    age: 30,
  },
  preferences: {
    newsletter: true,
    tags: ["tech", "programming"],
  },
});

// Update values reactively
data.user.name = "Bob"; // Changes are tracked
data.preferences.tags.push("javascript");

// Generate FormData for submission
const formData = getFormData();
// formData contains: user[name]=Bob, user[email]=alice@example.com, etc.

File Upload Example

// Handle file inputs with full type safety
document.getElementById("avatar").addEventListener("change", (e) => {
  const file = e.target.files[0];

  const { data, getFormData } = frmz({
    profile: {
      name: "John Doe",
      avatar: file, // File object handled properly
      documents: [file], // Works in arrays too
      metadata: {
        uploadDate: new Date().toISOString(),
      },
    },
  });

  // Submit to server
  fetch("/api/upload", {
    method: "POST",
    body: getFormData(), // Contains the file properly
  });
});

Advanced Schema Validation

import { z } from "zod";
import { frmz } from "frmz";

const userSchema = z.object({
  name: z.string().min(2),
  email: z.string().email(),
  avatar: z.instanceof(Blob).optional(),
  age: z.number().min(18),
  tags: z.array(z.string()),
});

const { data, getFormData } = frmz(
  {
    name: "Alice",
    email: "alice@example.com",
    age: 25,
    tags: ["developer"],
    avatar: someFile, // Optional blob
  },
  userSchema // Custom schema override
);

API Reference

1. frmz(initialData)

Creates a form manager with inferred schema.

Parameters:

• initialData: Object or array to use as initial state

Returns:

• data: Reactive proxy of the initial data
• getFormData(): FormData: Function that returns current state as FormData

2. frmz(initialData, schema)

Creates a form manager with custom Zod schema.

Parameters:

• initialData: Data matching the provided schema
• schema: Zod schema for validation

Returns:

• data: Reactive proxy of validated data
• getFormData(): FormData: Function that returns current state as FormData

Reactive Data Pattern

The data object is a deep proxy that tracks changes:

const { data, getFormData } = frmz({
  user: { name: "Alice", settings: { darkMode: true } },
});

// All changes are tracked
data.user.name = "Bob"; // Simple property
data.user.settings.darkMode = false; // Nested property
data.user.settings.fontSize = 16; // New properties

// getFormData() captures all current changes
const formData = getFormData(); // Contains latest state

FormData Output Format

The generated FormData uses standard encoding:

Object properties:

user[name]=Alice
user[email]=alice@example.com

Array elements:

tags[0]=tech
tags[1]=programming

File uploads:

tags[0]=tech
tags[1]=programming

## Type Utilities DeepWritable<T> Utility type to make deeply nested readonly types writable:

import type { DeepWritable } from "frmz";

type User = DeepWritable<typeof userSchema>;
// Now all properties are mutable

Error Handling

The library throws Zod validation errors when provided data doesn't match the schema:

try {
  const manager = frmz(
    { email: "invalid-email" },
    z.object({ email: z.string().email() })
  );
} catch (error) {
  console.error("Validation failed:", error.errors);
}

Common Use Cases

1. Form State Management

   const { data, getFormData } = frmz(initialFormState);
   
   // Bind to input events
   input.addEventListener("change", (e) => {
     data.user.name = e.target.value;
   });
   
   // Submit handler
   form.addEventListener("submit", async (e) => {
     e.preventDefault();
     await fetch("/submit", { body: getFormData() });
   });

2. File Upload Forms

   const { data, getFormData } = frmz({
     title: "",
     description: "",
     attachments: [], // Will hold files
   });
   
   // Add files to array
   fileInput.addEventListener("change", (e) => {
     data.attachments.push(...e.target.files);
   });

3. Configuration Objects

   const { data, getFormData } = frmz({
     settings: {
       theme: "dark",
       notifications: true,
       layout: { grid: true, spacing: 2 },
     },
   });

Limitations

• Root Types: Only objects and arrays are supported as root values

• FormData Encoding: Uses standard multipart/form-data encoding (not JSON)

• Circular References: Not supported in the data structure

• Server Processing: Requires server-side support for bracket notation (e.g.,user[name])

 Browser Support

Works in all modern browsers that support:

• Proxy API (ES2015)

• FormData API

• Blob/File API

 Contributing

Found an issue? Want to add a feature? Please open an issue or PR on our GitHub repository.

 License

MIT License - feel free to use in your projects!