react-form-with-constraints
Advanced tools
Simple form validation for React
npm install react-form-with-constraintsCheck the changelog for breaking changes and fixes between releases.
⚠️ Client side validation is cosmetic, you should not rely on it to enforce security
<form>
<label for="email">Email:</label>
<input type="email" id="email" required>
<button type="submit">Submit</button>
</form>
The required HTML5 attribute specifies that the user must fill in a value, type="email" checks that the entered text looks like an email address.
Resources:
<FieldFeedback when="valueMissing">My custom error message</FieldFeedback><FieldFeedback when={value => ...}><FieldFeedback ... warning>, <FieldFeedback ... info>react-form-with-constraints-bootstrapreact-form-with-constraints-material-uireact-form-with-constraints-native<input type="password" name="password"
value={this.state.password} onChange={this.handleChange}
required pattern=".{5,}" />
<FieldFeedbacks for="password">
<FieldFeedback when="valueMissing" />
<FieldFeedback when="patternMismatch">
Should be at least 5 characters long
</FieldFeedback>
<FieldFeedback when={value => !/\d/.test(value)} warning>
Should contain numbers
</FieldFeedback>
<FieldFeedback when={value => !/[a-z]/.test(value)} warning>
Should contain small letters
</FieldFeedback>
<FieldFeedback when={value => !/[A-Z]/.test(value)} warning>
Should contain capital letters
</FieldFeedback>
</FieldFeedbacks>
CodePen basic Password example: https://codepen.io/tkrotoff/pen/BRGdqL (StackBlitz version)
React Native example (React classes):
| iOS | Android |
|---|---|
 |  |
Other examples from the examples directory:
The API works the same way as React Router:
<Router>
<Route exact path="/" component={Home} />
<Route path="/news" component={NewsFeed} />
</Router>
It is also inspired by AngularJS ngMessages.
If you had to implement validation yourself, you would end up with a global object that tracks errors for each field.
react-form-with-constraints works similarly.
It uses React context to share the FieldsStore object across FieldFeedbacks and FieldFeedback.
The API reads like this: "for field when constraint violation display feedback", example:
<FieldFeedbacks for="password">
<FieldFeedback when="valueMissing" />
<FieldFeedback when="patternMismatch">Should be at least 5 characters long</FieldFeedback>
</FieldFeedbacks>
for field "password"
when constraint violation "valueMissing" display <the HTML5 error message (*)>
when constraint violation "patternMismatch" display "Should be at least 5 characters long"
Async support works as follow:
<FieldFeedbacks for="username">
<Async
promise={checkUsernameAvailability} /* Function that returns a promise */
then={available => available ?
<FieldFeedback key="1" info style={{color: 'green'}}>Username available</FieldFeedback> :
<FieldFeedback key="2">Username already taken, choose another</FieldFeedback>
// Why key=*? Needed otherwise React gets buggy when the user rapidly changes the field
}
/>
</FieldFeedbacks>
Trigger validation:
function MyForm() {
const form = useRef(null);
async function handleChange({ target }) {
// Validates only the given fields and returns Promise<Field[]>
await form.current.validateFields(target);
}
async function handleSubmit(e) {
e.preventDefault();
// Validates the non-dirty fields and returns Promise<Field[]>
await form.current.validateForm();
if (form.current.isValid()) console.log('The form is valid');
else console.log('The form is invalid');
}
return (
<FormWithConstraints ref={form} onSubmit={handleSubmit} noValidate>
<input
name="username"
onChange={handleChange}
required minLength={3}
/>
<FieldFeedbacks for="username">
<FieldFeedback when="tooShort">Too short</FieldFeedback>
<Async
promise={checkUsernameAvailability}
then={available => available ?
<FieldFeedback key="1" info style={{color: 'green'}}>Username available</FieldFeedback> :
<FieldFeedback key="2">Username already taken, choose another</FieldFeedback>
}
/>
<FieldFeedback when="*" />
</FieldFeedbacks>
</FormWithConstraints>
);
}
Important note:
If a field (i.e an <input>) does not have a matching FieldFeedbacks, the library won't known about this field (and thus won't perform validation).
The field name should match FieldFeedbacks.for:
<input name="MY_FIELD" ...>
<FieldFeedbacks for="MY_FIELD">
...
</FieldFeedbacks>
for: string => reference to a name attribute (e.g <input name="username">), should be unique to the current formstop?: 'first' | 'first-error' | 'first-warning' | 'first-info' | 'no' =>
when to stop rendering FieldFeedbacks, by default stops at the first error encountered (FieldFeedbacks order matters)Note: you can place FieldFeedbacks anywhere, have as many as you want for the same field, nest them, mix them with FieldFeedback... Example:
<input name="username" ... />
<FieldFeedbacks for="username" stop="first-warning">
<FieldFeedbacks>
<FieldFeedback ... />
<Async ... />
<FieldFeedbacks stop="first-info">
...
</FieldFeedbacks>
</FieldFeedbacks>
<FieldFeedback ... />
<Async ... />
</FieldFeedbacks>
<FieldFeedbacks for="username" stop="no">
...
</FieldFeedbacks>
when?:
ValidityState as a string => HTML5 constraint violation name'*' => matches any HTML5 constraint violation'valid' => displays the feedback only if the field is valid(value: string) => boolean => custom constrainterror?: boolean => treats the feedback as an error (default)warning?: boolean => treats the feedback as a warninginfo?: boolean => treats the feedback as an infochildren => what to display when the constraint matches; if missing, displays the HTML5 error message if anyAsync<T> => Async version of FieldFeedback (similar API as react-promise)
promise: (value: string) => Promise<T> => a promise you want to wait forpending?: React.ReactNode => runs when promise is pendingthen?: (value: T) => React.ReactNode => runs when promise is resolvedcatch?: (reason: any) => React.ReactNode => runs when promise is rejectedvalidateFields(...inputsOrNames: Array<Input | string>): Promise<Field[]> =>
Should be called when a field changes, will re-render the proper FieldFeedbacks (and update the internal FieldsStore).
Without arguments, all fields ($('[name]')) are validated.
validateFieldsWithoutFeedback(...inputsOrNames: Array<Input | string>): Promise<Field[]> =>
Validates only all non-dirty fields (won't re-validate fields that have been already validated with validateFields()),
If you want to force re-validate all fields, use validateFields().
Might be renamed to validateNonDirtyFieldsOnly() or validateFieldsNotDirtyOnly() in the future?
validateForm(): Promise<Field[]> =>
Same as validateFieldsWithoutFeedback() without arguments, typically called before to submit the form.
Might be removed in the future?
isValid(): boolean => should be called after validateFields(), validateFieldsWithoutFeedback() or validateForm(), indicates if the fields are valid
hasFeedbacks(): boolean => indicates if any of the fields have any kind of feedback
resetFields(...inputsOrNames: Array<Input | string>): Field[] =>
Resets the given fields and re-render the proper FieldFeedbacks.
Without arguments, all fields ($('[name]')) are reset.
Field =>
{
name: string;
validations: { // FieldFeedbackValidation[]
key: number;
type: 'error' | 'warning' | 'info' | 'whenValid';
show: boolean | undefined;
}[];
isValid: () => boolean
}
If you want to style <input>, use <Input> instead: it will add classes is-pending, has-errors, has-warnings, has-infos and/or is-valid on <input> when the field is validated.
Example: <Input name="username" /> can generate <input name="username" class="has-errors has-warnings">
FYI react-form-with-constraints-bootstrap and react-form-with-constraints-material-ui already style the fields to match their respective frameworks.
react-form-with-constraints needs ValidityState which is supported by all modern browsers and IE 11.
It also needs a polyfill such as core-js to support IE 11, see React JavaScript Environment Requirements.
You can use HTML5 attributes like type="email", required, minlength...
<label htmlFor="email">Email</label>
<input type="email" name="email" id="email"
value={this.state.email} onChange={this.handleChange}
required />
<FieldFeedbacks for="email">
<FieldFeedback when="*" />
</FieldFeedbacks>
...and/or rely on when functions:
<label htmlFor="email">Email</label>
<input name="email" id="email"
value={this.state.email} onChange={this.handleChange} />
<FieldFeedbacks for="email">
<FieldFeedback when={value => value.length === 0}>Please fill out this field.</FieldFeedback>
<FieldFeedback when={value => !/\S+@\S+/.test(value)}>Invalid email address.</FieldFeedback>
</FieldFeedbacks>
In the last case you will have to manage translations yourself (see SignUp example).
type="hidden", readonly or disabled input won't trigger any HTML5 form constraint validation like required, see https://codepen.io/tkrotoff/pen/gdjVNvv0.19.1 (2022/07/22)
FAQs
Simple form validation for React
The npm package react-form-with-constraints receives a total of 626 weekly downloads. As such, react-form-with-constraints popularity was classified as not popular.
We found that react-form-with-constraints demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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