Form React

Production React form patterns. Default stack: React Hook Form + Zod.

Quick Start

npm install react-hook-form @hookform/resolvers zod

import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import { z } from 'zod';

// 1. Define schema
const schema = z.object({
  email: z.string().email('Invalid email'),
  password: z.string().min(8, 'Min 8 characters')
});

type FormData = z.infer<typeof schema>;

// 2. Use form
function LoginForm() {
  const { register, handleSubmit, formState: { errors } } = useForm<FormData>({
    resolver: zodResolver(schema),
    mode: 'onBlur' // Reward early, punish late
  });

  return (
    <form onSubmit={handleSubmit(data => console.log(data))}>
      <input {...register('email')} type="email" autoComplete="email" />
      {errors.email && <span>{errors.email.message}</span>}
      
      <input {...register('password')} type="password" autoComplete="current-password" />
      {errors.password && <span>{errors.password.message}</span>}
      
      <button type="submit">Sign in</button>
    </form>
  );
}

When to Use Which

Default: React Hook Form — Better performance for most React web apps.

Use TanStack Form when:

• Building cross-framework component libraries
• Need strict controlled component behavior
• Heavy async validation (username checks)
• React Native applications

React Hook Form Patterns

Basic Form

import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import { loginSchema, type LoginFormData } from './schemas';

export function LoginForm({ onSubmit }: { onSubmit: (data: LoginFormData) => void }) {
  const {
    register,
    handleSubmit,
    formState: { errors, isSubmitting, touchedFields }
  } = useForm<LoginFormData>({
    resolver: zodResolver(loginSchema),
    mode: 'onBlur',           // First validation on blur (punish late)
    reValidateMode: 'onChange' // Re-validate on change (real-time correction)
  });

  return (
    <form onSubmit={handleSubmit(onSubmit)} noValidate>
      <div className="form-field">
        <label htmlFor="email">Email</label>
        <input
          id="email"
          type="email"
          autoComplete="email"
          aria-invalid={!!errors.email}
          {...register('email')}
        />
        {touchedFields.email && errors.email && (
          <span role="alert">{errors.email.message}</span>
        )}
      </div>

      <div className="form-field">
        <label htmlFor="password">Password</label>
        <input
          id="password"
          type="password"
          autoComplete="current-password"
          aria-invalid={!!errors.password}
          {...register('password')}
        />
        {touchedFields.password && errors.password && (
          <span role="alert">{errors.password.message}</span>
        )}
      </div>

      <button type="submit" disabled={isSubmitting}>
        {isSubmitting ? 'Signing in...' : 'Sign in'}
      </button>
    </form>
  );
}

Reusable Form Field Component

// FormField.tsx
import { useFormContext } from 'react-hook-form';
import { ReactNode } from 'react';

interface FormFieldProps {
  name: string;
  label: string;
  type?: string;
  autoComplete?: string;
  hint?: string;
  required?: boolean;
  children?: ReactNode;
}

export function FormField({
  name,
  label,
  type = 'text',
  autoComplete,
  hint,
  required,
  children
}: FormFieldProps) {
  const {
    register,
    formState: { errors, touchedFields }
  } = useFormContext();

  const error = errors[name];
  const touched = touchedFields[name];
  const showError = touched && error;
  const showValid = touched && !error;

  return (
    <div className={`form-field ${showError ? 'error' : ''} ${showValid ? 'valid' : ''}`}>
      <label htmlFor={name}>
        {label}
        {required && <span aria-hidden="true">*</span>}
      </label>
      
      {hint && <span className="hint">{hint}</span>}
      
      {children || (
        <input
          id={name}
          type={type}
          autoComplete={autoComplete}
          aria-invalid={!!error}
          aria-describedby={error ? `${name}-error` : undefined}
          {...register(name)}
        />
      )}
      
      {showError && (
        <span id={`${name}-error`} role="alert" className="error-message">
          {error.message as string}
        </span>
      )}
    </div>
  );
}

Using FormProvider for Nested Components

// F

...