# React Form Validation

> Provide valuable, actionable feedback to your users with HTML5 form validation, via browser default behaviors or custom styles and JavaScript.

## Example

For custom CoreUI form validation messages, you'll need to add the `noValidate` boolean property to your `<CForm>`. This disables the browser default feedback tooltips, but still provides access to the form validation APIs in JavaScript. Try to submit the form below; our JavaScript will intercept the submit button and relay feedback to you. When attempting to submit, you'll see the `:invalid` and `:valid` styles applied to your form controls.

Custom feedback styles apply custom colors, borders, focus styles, and background icons to better communicate feedback.

```html
import React, { FormEvent, useState } from 'react'
import {
  CCol,
  CButton,
  CForm,
  CFormCheck,
  CFormFeedback,
  CFormInput,
  CFormLabel,
  CInputGroup,
  CInputGroupText,
  CFormSelect,
} from '@coreui/react'

export const ValidationExample = () => {
  const [validated, setValidated] = useState(false)
  const handleSubmit = (event: FormEvent<HTMLFormElement>) => {
    const form = event.currentTarget
    if (form.checkValidity() === false) {
      event.preventDefault()
      event.stopPropagation()
    }

    setValidated(true)
  }

  return (
    <CForm
      className="row g-3 needs-validation"
      noValidate
      validated={validated}
      onSubmit={handleSubmit}
    >
      <CCol md={4}>
        <CFormInput
          type="text"
          defaultValue="Mark"
          feedbackValid="Looks good!"
          id="validationCustom01"
          label="First name"
          required
        />
      </CCol>
      <CCol md={4}>
        <CFormInput
          type="text"
          defaultValue="Otto"
          feedbackValid="Looks good!"
          id="validationCustom02"
          label="First name"
          required
        />
      </CCol>
      <CCol md={4}>
        <CFormLabel htmlFor="validationCustomUsername">Username</CFormLabel>
        <CInputGroup className="has-validation">
          <CInputGroupText>@</CInputGroupText>
          <CFormInput
            type="text"
            aria-describedby="inputGroupPrependFeedback"
            feedbackValid="Please choose a username."
            id="validationCustomUsername"
            required
          />
        </CInputGroup>
      </CCol>
      <CCol md={6}>
        <CFormInput
          type="text"
          aria-describedby="validationCustom03Feedback"
          feedbackInvalid="Please provide a valid city."
          id="validationCustom03"
          label="City"
          required
        />
      </CCol>
      <CCol md={3}>
        <CFormSelect
          aria-describedby="validationCustom04Feedback"
          feedbackInvalid="Please select a valid state."
          id="validationCustom04"
          label="State"
          required
        >
          <option disabled>Choose...</option>
          <option>...</option>
        </CFormSelect>
      </CCol>
      <CCol md={3}>
        <CFormInput
          type="text"
          aria-describedby="validationCustom05Feedback"
          feedbackInvalid="Please provide a valid zip."
          id="validationCustom05"
          label="Zip"
          required
        />
      </CCol>
      <CCol xs={12}>
        <CFormCheck
          type="checkbox"
          id="invalidCheck"
          label="Agree to terms and conditions"
          required
        />
        <CFormFeedback invalid>You must agree before submitting.</CFormFeedback>
      </CCol>
      <CCol xs={12}>
        <CButton color="primary" type="submit">
          Submit form
        </CButton>
      </CCol>
    </CForm>
  )
}
```

## Browser defaults

Not interested in custom validation feedback messages or writing JavaScript to change form behaviors? All good, you can use the browser defaults. Try submitting the form below. Depending on your browser and OS, you'll see a slightly different style of feedback.

While these feedback styles cannot be styled with CSS, you can still customize the feedback text through JavaScript.

```html
import React from 'react'
import {
  CCol,
  CButton,
  CForm,
  CFormCheck,
  CFormInput,
  CFormLabel,
  CInputGroup,
  CInputGroupText,
  CFormSelect,
} from '@coreui/react'

export const ValidationBrowserDefaultsExample = () => {
  return (
    <CForm className="row g-3">
      <CCol md={4}>
        <CFormInput
          type="text"
          id="validationDefault01"
          label="First name"
          defaultValue="Mark"
          required
        />
      </CCol>
      <CCol md={4}>
        <CFormInput
          type="text"
          id="validationDefault02"
          label="Last name"
          defaultValue="Otto"
          required
        />
      </CCol>
      <CCol md={4}>
        <CFormLabel htmlFor="validationDefaultUsername">Username</CFormLabel>
        <CInputGroup>
          <CInputGroupText id="inputGroupPrepend02">@</CInputGroupText>
          <CFormInput
            type="text"
            id="validationDefaultUsername"
            defaultValue=""
            aria-describedby="inputGroupPrepend02"
            required
          />
        </CInputGroup>
      </CCol>
      <CCol md={6}>
        <CFormInput type="text" id="validationDefault03" label="City" required />
      </CCol>
      <CCol md={3}>
        <CFormSelect id="validationDefault04" label="State">
          <option disabled>Choose...</option>
          <option>...</option>
        </CFormSelect>
      </CCol>
      <CCol md={3}>
        <CFormInput type="text" id="validationDefault05" label="Zip" required />
      </CCol>
      <CCol xs={12}>
        <CFormCheck
          type="checkbox"
          id="invalidCheck"
          label="Agree to terms and conditions"
          required
        />
      </CCol>
      <CCol xs={12}>
        <CButton color="primary" type="submit">
          Submit form
        </CButton>
      </CCol>
    </CForm>
  )
}
```

## Custom validation

In case you require custom or server-side validation, you can indicate invalid and valid form fields with `invalid` and `valid` boolean properties.

For invalid fields, ensure that the invalid feedback/error message is associated with the relevant form field using `aria-describedby` (noting that this attribute allows more than one `id` to be referenced, in case the field already points to additional form text).

```html
import React from 'react'
import {
  CCol,
  CButton,
  CForm,
  CFormCheck,
  CFormFeedback,
  CFormInput,
  CFormLabel,
  CInputGroup,
  CInputGroupText,
  CFormSelect,
} from '@coreui/react'

export const ValidationCustomExample = () => {
  return (
    <CForm className="row g-3">
      <CCol md={4}>
        <CFormInput
          type="text"
          id="validationServer01"
          label="Email"
          feedback="Looks good!"
          defaultValue="name@surname.com"
          valid
          required
        />
      </CCol>
      <CCol md={4}>
        <CFormInput
          type="text"
          id="validationServer02"
          label="Repeat email"
          feedback="Looks good!"
          defaultValue="name@surname.com"
          valid
          required
        />
      </CCol>
      <CCol md={4}>
        <CFormLabel htmlFor="validationServerUsername">Username</CFormLabel>
        <CInputGroup className="has-validation">
          <CInputGroupText id="inputGroupPrepend03">@</CInputGroupText>
          <CFormInput
            type="text"
            id="validationServerUsername"
            feedback="Please choose a username."
            defaultValue=""
            aria-describedby="inputGroupPrepend03"
            invalid
            required
          />
        </CInputGroup>
      </CCol>
      <CCol md={6}>
        <CFormInput
          type="text"
          id="validationServer03"
          label="City"
          feedback="Please provide a valid city."
          invalid
          required
        />
      </CCol>
      <CCol md={3}>
        <CFormSelect
          id="validationServer04"
          label="State"
          feedback="Please provide a valid city."
          invalid
        >
          <option disabled>Choose...</option>
          <option>...</option>
        </CFormSelect>
      </CCol>
      <CCol md={3}>
        <CFormInput
          type="text"
          id="validationServer05"
          label="zip"
          feedback="Please provide a valid zip."
          invalid
          required
        />
      </CCol>
      <CCol xs={12}>
        <CFormCheck
          type="checkbox"
          id="invalidCheck"
          label="Agree to terms and conditions"
          invalid
          required
        />
        <CFormFeedback invalid>You must agree before submitting.</CFormFeedback>
      </CCol>
      <CCol xs={12}>
        <CButton color="primary" type="submit">
          Submit form
        </CButton>
      </CCol>
    </CForm>
  )
}
```

## Supported elements

Validation styles are available for the following form controls and components:

- `<CFormCheck>`s
- `<CFormInput>`s
- `<CFormSelect>`s
- `<CFormTextarea>`s

```html
import React from 'react'
import { CButton, CForm, CFormCheck, CFormInput, CFormSelect, CFormTextarea } from '@coreui/react'

export const ValidationSupportedElementsExample = () => {
  return (
    <CForm validated={true}>
      <div className="mb-3">
        <CFormTextarea
          feedbackInvalid="Please enter a message in the textarea."
          id="validationTextarea"
          label="Textarea"
          placeholder="Required example textarea"
          required
        ></CFormTextarea>
      </div>
      <CFormCheck
        className="mb-3"
        id="validationFormCheck1"
        label="Check this checkbox"
        feedbackInvalid="Example invalid feedback text"
        required
      />
      <CFormCheck
        type="radio"
        name="radio-stacked"
        id="validationFormCheck2"
        label="Check this checkbox"
        required
      />
      <CFormCheck
        className="mb-3"
        type="radio"
        name="radio-stacked"
        id="validationFormCheck3"
        label="Or toggle this other radio"
        feedbackInvalid="More example invalid feedback text"
        required
      />
      <div className="mb-3">
        <CFormSelect
          feedbackInvalid="Example invalid select feedback"
          aria-label="select example"
          required
        >
          <option selected value="">
            Open this select menu
          </option>
          <option value="1">One</option>
          <option value="2">Two</option>
          <option value="3">Three</option>
        </CFormSelect>
      </div>
      <div className="mb-3">
        <CFormInput
          type="file"
          id="validationTextarea"
          feedbackInvalid="Example invalid form file feedback"
          aria-label="file example"
          required
        />
      </div>
      <div className="mb-3">
        <CButton type="submit" color="primary" disabled>
          Submit form
        </CButton>
      </div>
    </CForm>
  )
}
```

## Tooltips

If your form layout allows it, you can swap the text for the tooltip to display validation feedback in a styled tooltip. Be sure to have a parent with `position: relative` on it for tooltip positioning. In the example below, our column classes have this already, but your project may require an alternative setup.

```html
import React, { FormEvent, useState } from 'react'
import {
  CCol,
  CButton,
  CForm,
  CFormInput,
  CFormLabel,
  CInputGroup,
  CInputGroupText,
  CFormSelect,
} from '@coreui/react'

export const ValidationTooltipsExample = () => {
  const [validated, setValidated] = useState(false)
  const handleSubmit = (event: FormEvent<HTMLFormElement>) => {
    const form = event.currentTarget
    if (form.checkValidity() === false) {
      event.preventDefault()
      event.stopPropagation()
    }

    setValidated(true)
  }

  return (
    <CForm
      className="row g-3 needs-validation"
      noValidate
      validated={validated}
      onSubmit={handleSubmit}
    >
      <CCol md={4} className="position-relative">
        <CFormInput
          type="text"
          defaultValue="Mark"
          feedbackValid="Looks good!"
          id="validationTooltip01"
          label="First name"
          required
          tooltipFeedback
        />
      </CCol>
      <CCol md={4} className="position-relative">
        <CFormInput
          type="text"
          defaultValue="Otto"
          feedbackValid="Looks good!"
          id="validationTooltip02"
          label="First name"
          required
          tooltipFeedback
        />
      </CCol>
      <CCol md={4} className="position-relative">
        <CFormLabel htmlFor="validationTooltipUsername">Username</CFormLabel>
        <CInputGroup className="has-validation">
          <CInputGroupText id="inputGroupPrepend">@</CInputGroupText>
          <CFormInput
            type="text"
            aria-describedby="inputGroupPrependFeedback"
            feedbackInvalid="Please choose a username."
            id="validationTooltipUsername"
            required
            tooltipFeedback
          />
        </CInputGroup>
      </CCol>
      <CCol md={6} className="position-relative">
        <CFormInput
          type="text"
          aria-describedby="validationTooltip03Feedback"
          feedbackInvalid="Please provide a valid city."
          id="validationTooltip03"
          label="City"
          required
          tooltipFeedback
        />
      </CCol>
      <CCol md={3} className="position-relative">
        <CFormSelect
          aria-describedby="validationTooltip04Feedback"
          feedbackInvalid="Please select a valid state."
          id="validationTooltip04"
          label="State"
          required
          tooltipFeedback
        >
          <option selected disabled value="">
            Choose...
          </option>
          <option>...</option>
        </CFormSelect>
      </CCol>
      <CCol md={3} className="position-relative">
        <CFormInput
          type="text"
          aria-describedby="validationTooltip05Feedback"
          feedbackInvalid="Please provide a valid zip."
          id="validationTooltip05"
          label="Zip"
          required
          tooltipFeedback
        />
      </CCol>
      <CCol xs={12} className="position-relative">
        <CButton color="primary" type="submit">
          Submit form
        </CButton>
      </CCol>
    </CForm>
  )
}
```