This is the core package of haloform. It contains the schema builders, store, validation engine, dependency resolution, and multi-step form logic — all in pure TypeScript with zero runtime dependencies.

For React hooks, install @haloform/react. For React Native prop mappers, install @haloform/native.

Install

npm install @haloform/core @haloform/react

Quick Start

import { createForm, f } from "@haloform/core";
import { useForm } from "@haloform/react";

const loginSchema = createForm({
  email: f.email({ required: true }),
  password: f.text({ required: true, minLength: 8 }),
  remember: f.checkbox({ default: false }),
});

function LoginForm() {
  const { fields, handleSubmit } = useForm(loginSchema);

  return (
    <form onSubmit={handleSubmit((values) => console.log(values))}>
      <input
        value={fields.email.value}
        onChange={(e) => fields.email.onChange(e.target.value)}
        onBlur={fields.email.onBlur}
      />
      {fields.email.error && <span>{fields.email.error}</span>}

      <input
        type="password"
        value={fields.password.value}
        onChange={(e) => fields.password.onChange(e.target.value)}
        onBlur={fields.password.onBlur}
      />

      <button type="submit">Sign in</button>
    </form>
  );
}

Field Builders (f.*)

| Builder | Value Type | Extra Config | |---|---|---| | f.text() | string | minLength, maxLength, pattern | | f.email() | string | Built-in email format validation | | f.number() | number | min, max | | f.checkbox() | boolean | — | | f.select() | string | options (required) | | f.radio() | string | options (required) | | f.textarea() | string | minLength, maxLength | | f.date() | string | — |

All builders accept: required, default, validate, dependsOn.

Features

| Feature | Description | |---|---| | Schema-driven | Define fields with f.text(), f.email(), f.select(), etc. | | Built-in validation | Required, minLength, maxLength, min, max, email, pattern | | Async validation | Debounced with AbortController — stale requests auto-cancel | | Field dependencies | dependsOn for conditional visibility, dynamic options, cascading values | | Multi-step forms | createMultiStepForm with per-step validation and navigation | | Cross-field validation | Form-level validate(values) for password confirmation, etc. | | Full type inference | Schema infers { email: string, age: number, agreed: boolean } | | Zero dependencies | Pure TypeScript, ~5KB gzipped |

Async Validation

const schema = createForm({
  username: f.text({
    required: true,
    validate: async (value, signal) => {
      const res = await fetch(`/api/check-username?u=${value}`, { signal });
      const { available } = await res.json();
      return available ? true : "Username is taken";
    },
  }),
});

The async validator receives an AbortSignal — if the user types again before the previous check completes, it's automatically cancelled.

Field Dependencies

const schema = createForm({
  country: f.select({ options: ["US", "PE", "PT"], required: true }),
  state: f.select({
    options: [],
    dependsOn: {
      country: (value) => ({
        visible: value === "US",
        options: value === "US" ? ["CA", "NY", "TX"] : [],
      }),
    },
  }),
});

Multi-Step Forms

import { createMultiStepForm, f } from "@haloform/core";

const checkoutSchema = createMultiStepForm([
  {
    name: "Shipping",
    fields: {
      name: f.text({ required: true }),
      address: f.text({ required: true }),
    },
  },
  {
    name: "Payment",
    fields: {
      card: f.text({ required: true, pattern: /^\d{16}$/ }),
      cvv: f.text({ required: true, minLength: 3 }),
    },
  },
]);

Architecture

@haloform/core          Pure TypeScript, zero deps
├── schema.ts           Field builders (f.*) + createForm
├── types.ts            Full type system with inference
├── store.ts            Subscribable state management
├── validation.ts       Sync/async + debounce + abort
├── dependencies.ts     Inter-field dependency resolution
└── multistep.ts        Multi-step navigation + per-step validation

Full Documentation

See the full documentation and examples on GitHub.

License

MIT — Made with care by Angel Orellana