Form validators

Premade validation functions

Usage

@mantine/form package exports several functions that can be used in validation rules object. Validation functions are tiny in size and provide basic validation, if you have complex validation requirements, use other types of validation.

import { useForm, isNotEmpty, isEmail, isInRange, hasLength, matches } from '@mantine/form';
import { Button, Group, TextInput, NumberInput, Box } from '@mantine/core';

function Demo() {
  const form = useForm({
    initialValues: {
      name: '',
      job: '',
      email: '',
      favoriteColor: '',
      age: 18,
    },

    validate: {
      name: hasLength({ min: 2, max: 10 }, 'Name must be 2-10 characters long'),
      job: isNotEmpty('Enter your current job'),
      email: isEmail('Invalid email'),
      favoriteColor: matches(/^#([0-9a-f]{3}){1,2}$/, 'Enter a valid hex color'),
      age: isInRange({ min: 18, max: 99 }, 'You must be 18-99 years old to register'),
    },
  });

  return (
    <Box component="form" maw={400} mx="auto" onSubmit={form.onSubmit(() => {})}>
      <TextInput label="Name" placeholder="Name" withAsterisk {...form.getInputProps('name')} />
      <TextInput
        label="Your job"
        placeholder="Your job"
        withAsterisk
        mt="md"
        {...form.getInputProps('job')}
      />
      <TextInput
        label="Your email"
        placeholder="Your email"
        withAsterisk
        mt="md"
        {...form.getInputProps('email')}
      />
      <TextInput
        label="Your favorite color"
        placeholder="Your favorite color"
        withAsterisk
        mt="md"
        {...form.getInputProps('favoriteColor')}
      />
      <NumberInput
        label="Your age"
        placeholder="Your age"
        withAsterisk
        mt="md"
        {...form.getInputProps('age')}
      />

      <Group justify="flex-end" mt="md">
        <Button type="submit">Submit</Button>
      </Group>
    </Box>
  );
}

Optional error

Last argument of all validator functions below is optional. If error is not set, then fields with failed validation will only have invalid styles without error message:

import { useForm, isNotEmpty, isEmail, isInRange, hasLength, matches } from '@mantine/form';
import { Button, Group, TextInput, NumberInput, Box } from '@mantine/core';

function Demo() {
  const form = useForm({
    initialValues: {
      name: '',
      job: '',
      email: '',
      favoriteColor: '',
      age: 18,
    },

    validate: {
      name: hasLength({ min: 2, max: 10 }),
      job: isNotEmpty(),
      email: isEmail(),
      favoriteColor: matches(/^#([0-9a-f]{3}){1,2}$/),
      age: isInRange({ min: 18, max: 99 }),
    },
  });

  return (
    <Box component="form" maw={400} mx="auto" onSubmit={form.onSubmit(() => {})}>
      <TextInput label="Name" placeholder="Name" withAsterisk {...form.getInputProps('name')} />
      <TextInput
        label="Your job"
        placeholder="Your job"
        withAsterisk
        mt="md"
        {...form.getInputProps('job')}
      />
      <TextInput
        label="Your email"
        placeholder="Your email"
        withAsterisk
        mt="md"
        {...form.getInputProps('email')}
      />
      <TextInput
        label="Your favorite color"
        placeholder="Your favorite color"
        withAsterisk
        mt="md"
        {...form.getInputProps('favoriteColor')}
      />
      <NumberInput
        label="Your age"
        placeholder="Your age"
        withAsterisk
        mt="md"
        {...form.getInputProps('age')}
      />

      <Group justify="flex-end" mt="md">
        <Button type="submit">Submit</Button>
      </Group>
    </Box>
  );
}

isNotEmpty

isNotEmpty checks that form value is not empty. Empty string, empty array, false, null and undefined values are considered to be empty. Strings are trimmed before validation.

import { isNotEmpty, useForm } from '@mantine/form';

const form = useForm({
  initialValues: {
    name: '',
    acceptTermsOfUse: false,
    country: null,
    previousJobs: [],
  },

  validate: {
    // Empty strings are considered to be invalid
    name: isNotEmpty('Name cannot be empty'),

    // False value is considered to be invalid
    acceptTermsOfUse: isNotEmpty('You must accept terms of use'),

    // null is considered to be invalid
    country: isNotEmpty('Pick your country'),

    // Empty arrays are considered to be invalid
    previousJobs: isNotEmpty('Enter at least one job'),
  },
});

isEmail

isEmail uses /^\w+([.-]?\w+)*@\w+([.-]?\w+)*(\.\w{2,})+$/ regexp to determine whether form value is an email:

import { isEmail, useForm } from '@mantine/form';

const form = useForm({
  initialValues: {
    email: '',
  },

  validate: {
    email: isEmail('Invalid email'),
  },
});

matches

matches checks whether form value matches given regexp. If form value is not a string, validation will be failed.

import { matches, useForm } from '@mantine/form';

const form = useForm({
  initialValues: {
    color: '',
  },

  validate: {
    color: matches(/^#([0-9a-f]{3}){1,2}$/, 'Invalid color'),
  },
});

isInRange

isInRange checks whether form value is within given min-max range. If form value is not a number, validation will be failed.

import { isInRange, useForm } from '@mantine/form';

const form = useForm({
  initialValues: {
    maxRange: 0,
    minRange: 0,
    minMaxRange: 0,
  },

  validate: {
    maxRange: isInRange({ max: 20 }, 'Value must be 20 or less'),
    minRange: isInRange({ min: 10 }, 'Value must be 10 or more'),
    minMaxRange: isInRange(
      { min: 10, max: 20 },
      'Value must be between 10 and 20'
    ),
  },
});

hasLength

hasLength check whether form value length is within given min-max range. hasLength will work correctly with strings, arrays and any other objects that have length property. Strings are trimmed before validation.

import { useForm, hasLength } from '@mantine/form';

const form = useForm({
  initialValues: {
    exact: '',
    maxLength: '',
    minLength: '',
    minMaxLength: '',
  },

  validate: {
    exact: hasLength(5, 'Values must have exactly 5 characters')
    maxLength: hasLength({ max: 20 }, 'Value must have 20 or less characters'),
    minLength: hasLength({ min: 10 }, 'Value must have 10  or more characters'),
    minMaxLength: hasLength({ min: 10, max: 20 }, 'Value must have 10-20 characters'),
  },
});

matchesField

matchesField checks whether form value is the same as value in other form field. Note that matchesField can only work with primitive values (arrays and objects cannot be compared).

import { matchesField, useForm } from '@mantine/form';

const form = useForm({
  initialValues: {
    password: '',
    confirmPassword: '',
  },

  validate: {
    confirmPassword: matchesField(
      'password',
      'Passwords are not the same'
    ),
  },
});