* Bump version to 5.3.0-alpha1 * Dist * Add docs versions updates * Update note in homepage hero Co-authored-by: Mark Otto <markdotto@gmail.com>
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layout | title | description | group | toc | extra_js | |||||
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docs | Validation | Provide valuable, actionable feedback to your users with HTML5 form validation, via browser default behaviors or custom styles and JavaScript. | forms | true |
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{{< callout warning >}} We are aware that currently the client-side custom validation styles and tooltips are not accessible, since they are not exposed to assistive technologies. While we work on a solution, we'd recommend either using the server-side option or the default browser validation method. {{< /callout >}}
How it works
Here's how form validation works with Bootstrap:
- HTML form validation is applied via CSS's two pseudo-classes,
:invalid
and:valid
. It applies to<input>
,<select>
, and<textarea>
elements. - Bootstrap scopes the
:invalid
and:valid
styles to parent.was-validated
class, usually applied to the<form>
. Otherwise, any required field without a value shows up as invalid on page load. This way, you may choose when to activate them (typically after form submission is attempted). - To reset the appearance of the form (for instance, in the case of dynamic form submissions using Ajax), remove the
.was-validated
class from the<form>
again after submission. - As a fallback,
.is-invalid
and.is-valid
classes may be used instead of the pseudo-classes for server-side validation. They do not require a.was-validated
parent class. - Due to constraints in how CSS works, we cannot (at present) apply styles to a
<label>
that comes before a form control in the DOM without the help of custom JavaScript. - All modern browsers support the constraint validation API, a series of JavaScript methods for validating form controls.
- Feedback messages may utilize the browser defaults (different for each browser, and unstylable via CSS) or our custom feedback styles with additional HTML and CSS.
- You may provide custom validity messages with
setCustomValidity
in JavaScript.
With that in mind, consider the following demos for our custom form validation styles, optional server-side classes, and browser defaults.
Custom styles
For custom Bootstrap form validation messages, you'll need to add the novalidate
boolean attribute to your <form>
. 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. Background icons for <select>
s are only available with .form-select
, and not .form-control
.
{{< example >}}
{{< example lang="js" show_preview="false" >}} {{< js.inline >}} {{- readFile (path.Join "site/static/docs" .Site.Params.docs_version "assets/js/validate-forms.js") -}} {{< /js.inline >}} {{< /example >}}
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.
{{< example >}}
Server-side
We recommend using client-side validation, but in case you require server-side validation, you can indicate invalid and valid form fields with .is-invalid
and .is-valid
. Note that .invalid-feedback
is also supported with these classes.
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).
To fix issues with border radius, input groups require an additional .has-validation
class.
{{< example >}}
Supported elements
Validation styles are available for the following form controls and components:
<input>
s and<textarea>
s with.form-control
(including up to one.form-control
in input groups)<select>
s with.form-select
.form-check
s
{{< example >}}
Tooltips
If your form layout allows it, you can swap the .{valid|invalid}-feedback
classes for .{valid|invalid}-tooltip
classes 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.
{{< example >}}
Sass
Variables
{{< scss-docs name="form-feedback-variables" file="scss/_variables.scss" >}}
Mixins
Two mixins are combined together, through our loop, to generate our form validation feedback styles.
{{< scss-docs name="form-validation-mixins" file="scss/mixins/_forms.scss" >}}
Map
This is the validation Sass map from _variables.scss
. Override or extend this to generate different or additional states.
{{< scss-docs name="form-validation-states" file="scss/_variables.scss" >}}
Maps of $form-validation-states
can contain three optional parameters to override tooltips and focus styles.
Loop
Used to iterate over $form-validation-states
map values to generate our validation styles. Any modifications to the above Sass map will be reflected in your compiled CSS via this loop.
{{< scss-docs name="form-validation-states-loop" file="scss/forms/_validation.scss" >}}
Customizing
Validation states can be customized via Sass with the $form-validation-states
map. Located in our _variables.scss
file, this Sass map is how we generate the default valid
/invalid
validation states. Included is a nested map for customizing each state's color, icon, tooltip color, and focus shadow. While no other states are supported by browsers, those using custom styles can easily add more complex form feedback.