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use-form

Manage forms state, handles values and validation
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@mantine/hooks

Usage

use-form provides bare minimum api to manage simple forms. It includes handlers to set and validate values. Hook does not depend on @mantine/core inputs and does not work with dom.

import { TextInput, Button } from '@mantine/core';
import { useForm } from '@mantine/hooks';


export function Demo() {
  const form = useForm({
    initialValues: {
      email: '',
      termsOfService: false,
    },


    validationRules: {
      email: (value) => /^\S+@\S+$/.test(value),
    },
  });


  return (
    <form onSubmit={form.onSubmit((values) => console.log(values))}>
      <TextInput
        required
        label="Email"
        error={form.errors.email && 'Please specify valid email'}
        value={form.values.email}
        onChange={(event) => form.setFieldValue('email', event.currentTarget.value)}
      />


      <TextInput
        label="Name"
        value={form.values.name}
        onChange={(event) => form.setFieldValue('name', event.currentTarget.value)}
      />


      <Button type="submit">Submit</Button>
    </form>
  );
}

API

use-form hook accepts configuration object as single argument:

  • initialValues – object with initial form values
  • validationRules – objects of functions that will be used to validate form values

Hook returns object with properties:

  • values – current form values
  • setValues – React useState hook setState action to set values
  • setFieldValue – function to set value of single field
  • validate – function to validate all values with validationRules
  • validateField – function to validate single field value with validationRules
  • errors – object of booleans which contains results of running validationRules functions on corresponding fields
  • setFieldError – function to set single field error in errors
  • resetErrors – function to set all errors to false
  • setErrors – React useState hook setState action to set errors
  • reset – function to reset all values and errors to initial state
  • onSubmit – wrapper function for form onSubmit event handler

initialValues

initialValues is required for any form and defines form.values shape. When form is reset with form.reset function these values are set to form.values.

validationRules

validationRules is an optional object of functions which are used to validate form.values. If you do not need validation in your form, you can skip them:

// Form without validation
const form = useForm({ initialValues: { name: '', age: 0 } });

validationRules must include only keys from initialValues, keys from initialValues that do not have corresponding validation rule will always be considered valid.

// validation will run only on name field
const form = useForm({
  initialValues: {
    name: '',
    age: 0, // age field is always valid
  },
  validationRules: {
    // imposter validation rule is noop and will be ignored, ts will complain
    imposter: (value) => value.trim().length >= 2,
    name: (value) => value.trim().length >= 2,
  },
});

form.values

values contains current values of form, it has the same shape as initialValues:

const form = useForm({ initialValues: { name: '', age: 0 } });
form.values; // -> { name: '', age: 0 }


form.setFieldValue('name', 'Bob');
form.values; // -> { name: 'Bob', age: 0 }

form.setFieldValue

setFieldValue function sets value at given key on values object:

const form = useForm({ initialValues: { name: '', age: 0 } });


form.setFieldValue('name', 'Bob');
form.setFieldValue('age', 25);
form.values; // -> { name: 'Bob', age: 25 }

Usually this function is used to work with input elements:

const form = useForm({ initialValues: { name: '' } });


const input = (
  <input
    value={form.values.name}
    onChange={(event) => form.setFieldValue('name', event.currentTarget.value)}
  />
);

form.setValues

setValues allows you to set all values with single function call:

const form = useForm({ initialValues: { name: '', age: 0 } });


// setValues with object
form.setValues({ name: 'Bob', age: 25 });
form.values; // -> { name: 'Bob', age: 25 }


// setValues with callback
form.setValues((currentValues) => ({ ...currentValues, age: currentValues.age + 10 }));
form.values; // -> { name: 'Bob', age: 35 }

form.validate

validate function runs all validation rules on corresponding values key:

const form = useForm({
  initialValues: { name: '', age: 0 },
  validationRules: {
    name: (value) => value.trim().length >= 2,
  },
});


form.errors; // -> { name: false, age: false }


form.validate();
form.errors; // -> { name: true, age: false }


form.setFieldValue('name', 'Bob');
form.validate();
form.errors; // -> { name: false, age: false }

form.validateField

validateField function allows you to run validations for individual fields, for example, it can be useful if you want to validate field when it loses focus:

const form = useForm({
  initialValues: { name: '', age: 0 },
  validationRules: {
    name: (value) => value.trim().length >= 2,
    age: (value) => value >= 18,
  },
});


form.setFieldValue('age', 12);
form.validateField('age');
form.errors; // -> { age: true, name: false }


form.validateField('name');
form.errors; // -> { age: true, name: true }

form.setFieldError

setFieldError allows you to bypass validation and manipulate errors object as you wish. For example, you can remove error from field once it was focused or perform your own validation:

const form = useForm({
  initialValues: { name: '', age: 0 },
  validationRules: {
    name: (value) => value.trim().length >= 2,
  },
});


form.errors; // -> { name: false, age: false }


form.setFieldError('name', true);
form.errors; // -> { name: true, age: false }


form.setFieldError('name', true);
form.errors; // -> { name: false, age: false }

form.setErrors

setErrors sets errors object. Use it when external fields validation occurs, e.g. on server:

const form = useForm({ initialValues: { name: '', age: 0 } });
form.errors; // -> { name: false, age: false }


// You can set errors with object
form.setErrors({ name: true, age: true });
form.errors; // -> { name: true, age: true }


// or with callback
form.setErrors((errors) => ({
  name: !errors.name,
  age: !errors.age,
}));
form.errors; // -> { name: false, age: false }

form.resetErrors

resetErrors sets all errors to false:

const form = useForm({ initialValues: { name: '', age: 0 } });
form.errors; // -> { name: false, age: false }


form.setErrors({ name: true, age: true });
form.errors; // -> { name: true, age: true }


form.resetErrors();
form.errors; // -> { name: false, age: false }

form.reset

reset function sets all errors to false and sets values to initialValues:

const form = useForm({ initialValues: { name: '', age: 0 } });
form.setErrors({ name: true, age: true });
form.setValues({ name: 'Bob', age: 25 });


form.errors; // -> { name: true, age: true }
form.values; // -> { name: 'Bob', age: 25 }


form.reset();
form.errors; // -> { name: false, age: false }
form.values; // -> { name: '', age: 0 }

form.onSubmit:

onSubmit takes function as an argument and calls it with values if form has no validation errors:

const form = useForm({
  initialValues: { name: '', age: 0 },
  validationRules: {
    name: (value) => value.trim().length >= 2,
  },
});


// console.log will be called with form.values only if
// form.validate does not encounter errors
const authForm = <form onSubmit={form.onSubmit((values) => console.log(values))} />;

Examples


Validate field on blur

import { TextInput } from '@mantine/core';
import { useForm } from '@mantine/hooks';


export function Demo() {
  const form = useForm({
    initialValues: { email: '' },
    validationRules: {
      email: (value) => /^\S+@\S+$/.test(value),
    },
  });


  return (
    <TextInput
      required
      label="Email"
      error={form.errors.email && 'Please specify valid email'}
      value={form.values.email}
      onChange={(event) => form.setFieldValue('email', event.currentTarget.value)}
      onBlur={() => form.validateField('email')}
    />
  );
}

External field validation

Submit form with test@mantine.dev email to see external validation error:

import { useState } from 'react';
import { TextInput, Button } from '@mantine/core';
import { useForm } from '@mantine/hooks';


export function Demo() {
  const [loading, setLoading] = useState(false);
  const [serverError, setServerError] = useState<string>(null);
  const form = useForm({
    initialValues: { email: 'test@mantine.dev' },
    validationRules: {
      email: (value) => /^\S+@\S+$/.test(value),
    },
  });


  const handleSubmit = (values: typeof form['values']) => {
    setLoading(true);
    setTimeout(() => {
      setLoading(false);
      if (values.email === 'test@mantine.dev') {
        setServerError('Email already taken');
        form.setFieldError('email', true);
      }
    }, 1500);
  };


  return (
    <form onSubmit={form.onSubmit(handleSubmit)} style={{ position: 'relative' }}>
      <LoadingOverlay visible={loading} />
      <TextInput
        required
        label="Email"
        placeholder="your@email.com"
        error={form.errors.email && (serverError || 'Please specify valid email')}
        value={form.values.email}
        onChange={(event) => form.setFieldValue('email', event.currentTarget.value)}
        onFocus={() => {
          setServerError(null);
          form.setFieldError('email', false);
        }}
      />


      <Button type="submit">Register</Button>
    </form>
  );
}

Authentication form

Browse code on Github

import React, { useState } from 'react';
import { useForm } from '@mantine/hooks';
import { EnvelopeClosedIcon, LockClosedIcon } from '@modulz/radix-icons';
import {
  TextInput,
  PasswordInput,
  Group,
  Checkbox,
  Button,
  Paper,
  Text,
  LoadingOverlay,
  useMantineTheme,
} from '../../src';


export interface AuthenticationFormProps {
  noShadow?: boolean;
  noPadding?: boolean;
  noSubmit?: boolean;
  style?: React.CSSProperties;
}


export function AuthenticationForm({
  noShadow,
  noPadding,
  noSubmit,
  style,
}: AuthenticationFormProps) {
  const [formType, setFormType] = useState<'register' | 'login'>('register');
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<string>(null);
  const theme = useMantineTheme();
  const inputVariant = theme.colorScheme === 'dark' ? 'filled' : 'default';


  const toggleFormType = () => {
    setFormType((current) => (current === 'register' ? 'login' : 'register'));
    setError(null);
  };


  const form = useForm({
    initialValues: {
      firstName: '',
      lastName: '',
      email: '',
      password: '',
      termsOfService: true,
    },


    validationRules: {
      firstName: (value) => formType === 'login' || value.trim().length >= 2,
      lastName: (value) => formType === 'login' || value.trim().length >= 2,
      email: (value) => /^\S+@\S+$/.test(value),
      password: (value) => /^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{6,}$/.test(value),
    },
  });


  const handleSubmit = () => {
    setLoading(true);
    setError(null);
    setTimeout(() => {
      setLoading(false);
      setError(
        formType === 'register'
          ? 'User with this email already exists'
          : 'User with this email does not exist'
      );
    }, 3000);
  };


  return (
    <Paper
      padding={noPadding ? 0 : 'lg'}
      shadow={noShadow ? null : 'sm'}
      style={{
        position: 'relative',
        backgroundColor: theme.colorScheme === 'dark' ? theme.colors.dark[7] : theme.white,
        ...style,
      }}
    >
      <form onSubmit={form.onSubmit(handleSubmit)}>
        <LoadingOverlay visible={loading} />
        {formType === 'register' && (
          <div style={{ display: 'flex', marginBottom: 15 }}>
            <TextInput
              data-autofocus
              required
              placeholder="Your first name"
              label="First name"
              style={{ marginRight: 20, flex: '0 0 calc(50% - 10px)' }}
              value={form.values.firstName}
              onChange={(event) => form.setFieldValue('firstName', event.currentTarget.value)}
              onFocus={() => form.setFieldError('firstName', false)}
              error={form.errors.firstName && 'First name should include at least 2 characters'}
              variant={inputVariant}
            />


            <TextInput
              required
              placeholder="Your last name"
              label="Last name"
              style={{ flex: '0 0 calc(50% - 10px)' }}
              value={form.values.lastName}
              onChange={(event) => form.setFieldValue('lastName', event.currentTarget.value)}
              onFocus={() => form.setFieldError('lastName', false)}
              error={form.errors.lastName && 'Last name should include at least 2 characters'}
              variant={inputVariant}
            />
          </div>
        )}


        <TextInput
          required
          placeholder="Your email"
          label="Email"
          icon={<EnvelopeClosedIcon />}
          value={form.values.email}
          onChange={(event) => form.setFieldValue('email', event.currentTarget.value)}
          onFocus={() => form.setFieldError('email', false)}
          error={form.errors.email && 'Field should contain a valid email'}
          variant={inputVariant}
        />


        <PasswordInput
          style={{ marginTop: 15 }}
          required
          placeholder="Password"
          label="Password"
          showPasswordLabel="Show password"
          hidePasswordLabel="Hide password"
          icon={<LockClosedIcon />}
          value={form.values.password}
          onChange={(event) => form.setFieldValue('password', event.currentTarget.value)}
          onFocus={() => form.setFieldError('password', false)}
          variant={inputVariant}
          error={
            form.errors.password &&
            'Password should contain 1 number, 1 letter and at least 6 characters'
          }
        />


        {formType === 'register' && (
          <Checkbox
            style={{ marginTop: 20 }}
            label="I agree to sell my soul and privacy to this corporation"
            checked={form.values.termsOfService}
            onChange={(event) => form.setFieldValue('termsOfService', event.currentTarget.checked)}
          />
        )}


        {error && (
          <Text color="red" size="sm" style={{ marginTop: 10 }}>
            {error}
          </Text>
        )}


        {!noSubmit && (
          <Group position="apart" style={{ marginTop: 25 }}>
            <Button variant="link" color="gray" onClick={toggleFormType} size="sm">
              {formType === 'register'
                ? 'Have an account? Login'
                : "Don't have an account? Register"}
            </Button>


            <Button color="blue" type="submit">
              {formType === 'register' ? 'Register' : 'Login'}
            </Button>
          </Group>
        )}
      </form>
    </Paper>
  );
}

TypeScript

Definition

function useForm<T extends { [key: string]: any }>(configuration: {
  initialValues: T;
  validationRules?: {
    [P in keyof T]?: (value: T[P]) => boolean;
  };
}): {
  values: T;
  errors: Record<keyof T, boolean>;
  validate: () => boolean;
  reset: () => void;
  resetErrors: () => void;
  setValues: React.Dispatch<React.SetStateAction<T>>;
  setErrors: React.Dispatch<React.SetStateAction<Record<keyof T, boolean>>>;
  setFieldValue: <K extends keyof T, U extends T[K]>(field: K, value: U) => void;
  setFieldError: (field: keyof T, error: boolean) => void;
  validateField: (field: keyof T) => void;
  onSubmit: (handleSubmit: (values: T) => any) => (event?: React.FormEvent) => void;
};

Set values type

use-form will use values types from initialValues, but you can pass your own type:

const form = useForm<{ name?: string; termsOfService?: boolean }>({
  initialValues: {
    name: '',
    termsOfService: false,
  },
});

Get form values type

Use typeof to get form values type:

const form = useForm({ initialValues: { email: '' } });


const handleSubmit = (values: typeof form['values']) => {
  // values – { email: string }
};
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