Validation with yup

Validate fields before submit with yup and fetchit:before. Example: name and age.

Important!

Client-side validation is not secure and should only be used to improve user experience.

Markup

novalidate disables browser validation. For AJAX, add [data-success] and [data-validation-error].

modx

<form action="[[~[[*id]]]]" method="post" novalidate>
  <label> Name
    <input type="text" name="name" value="[[+fi.name]]" />
    <span data-error="name">[[+fi.error.name]]</span>
  </label>
  <label> Age
    <input type="text" name="age" value="[[+fi.age]]" />
    <span data-error="age">[[+fi.error.age]]</span>
  </label>
  <div role="alert" data-success style="display: none;"></div>
  <div role="alert" data-validation-error style="display: none;"></div>
  <button type="submit">Submit</button>
</form>

fenom

<form action="{$_modx->resource.id | url}" method="post" novalidate>
  <label> Name
    <input type="text" name="name" value="{$_modx->getPlaceholder('fi.name')}" />
    <span data-error="name">{$_modx->getPlaceholder('fi.error.name')}</span>
  </label>
  <label> Age
    <input type="text" name="age" value="{$_modx->getPlaceholder('fi.age')}" />
    <span data-error="age">{$_modx->getPlaceholder('fi.error.age')}</span>
  </label>
  <div role="alert" data-success style="display: none;"></div>
  <div role="alert" data-validation-error style="display: none;"></div>
  <button type="submit">Submit</button>
</form>

Setup

ESM from CDN:

<script type="module">
  import * as yup from 'https://cdn.jsdelivr.net/npm/yup@1/+esm'
</script>

Handler

yup schema, validateSync with abortEarly: false, errors via setError. Optional toast via FetchIt.Message (notifications):

<script type="module">
  import * as yup from 'https://cdn.jsdelivr.net/npm/yup@1/+esm'

  document.addEventListener('fetchit:before', (e) => {
    const { formData, fetchit } = e.detail
    const fields = Object.fromEntries(formData.entries())

    const formSchema = yup.object({
      name: yup
        .string()
        .required('Enter your name'),
      age: yup
        .number()
        .required('Enter your age')
        .min(18, 'You must be at least 18')
        .integer()
        .typeError('Field must be a number'),
    })

    try {
      formSchema.validateSync(fields, { abortEarly: false })
    } catch (err) {
      e.preventDefault()

      for (const { path, message } of err.inner) {
        fetchit.setError(path, message)
      }

      FetchIt.Message?.error?.('Fix the form errors')
    }
  })
</script>

Localizing yup messages

Set error text in the schema (as above) or via the yup localization API. See error message customization.

Mirror rules on the server in FormIt:

modx

[[!FetchIt?
  &form=`form.tpl`
  &hooks=`email,FormItSaveForm`
  &validate=`name:required,age:required:isNumber:minValue=^18^`
]]

fenom

{'!FetchIt' | snippet : [
  'form' => 'form.tpl',
  'hooks' => 'email,FormItSaveForm',
  'validate' => 'name:required,age:required:isNumber:minValue=^18^',
]}

FormIt validators: FormIt documentation.