How can I auto-validate prefilled lazy-loaded date fields in Vue.js?

You can “touch” or trigger validation on the date field after you prefill its value so that the lazy validation gets run without explicit user interaction. One approach is to add a ref to your v-text-field and then, after you autofill the date, programmatically dispatch a blur or input event so that Vuetify’s lazy validation picks up the new value.

Below is an example of how you might modify your component:

Template

Add a ref (e.g. ratingPeriodBeginInput) to your v-text-field so you can reference it later:

VUECopied
<v-menu
  v-model="ratingPeriodBeginMenu"
  :close-on-content-click="false"
  transition="scale-transition"
  offset-y
  max-width="290px"
  min-width="auto"
>
  <template v-slot:activator="{ props }">
    <v-text-field
      ref="ratingPeriodBeginInput"
      color="primary"
      v-bind="props"
      label="Rating Period Begin Date"
      :model-value="formatDate(ratingPeriodBeginModel, 'MM/DD/YYYY')?.toString()"
      prepend-inner-icon="mdi-calendar"
      :rules="objectRequiredRule"
      validate-on="lazy input"
      readonly
      variant="outlined"
    />
  </template>
  <v-date-picker
    v-model="ratingPeriodBeginModel"
    :max="ratingPeriodEndModel"
    color="primary"
    no-title
    @update:modelValue="ratingPeriodBeginMenu = false"
  />
</v-menu>

Script

After autofilling the date (for example in a method or in a watcher), call the validation by dispatching a blur event. Using Vue’s nextTick ensures the DOM has updated with the new value.

JAVASCRIPTCopied
import { ref, nextTick } from 'vue'
import dayjs from 'dayjs'

const ratingPeriodBeginModel = ref(null)
const ratingPeriodBeginMenu = ref(false)
const objectRequiredRule = [(value) => !!value || 'Required.']

// Assume this ref is linked to our v-text-field:
const ratingPeriodBeginInput = ref(null)

function autoFillDates(rateSubmission) {
  // Autofill the date
  ratingPeriodBeginModel.value = dayjs(rateSubmission?.form_data.rate_date_start).toDate()
  
  // Wait for the input to update, then trigger validation by simulating a blur event
  nextTick(() => {
    // You can dispatch a blur event to ensure validation runs
    if (ratingPeriodBeginInput.value?.$el) {
      ratingPeriodBeginInput.value.$el.dispatchEvent(new Event('blur'))
    }
  })
}

Explanation

• Adding a Ref: By adding a ref (here, ratingPeriodBeginInput) on your v-text-field, you can later reference the underlying element.
• Simulating a Blur: Once you prefill the date with your auto fill function, wrap a call in nextTick to guarantee the new value is rendered. Then dispatch a blur event on the input element so that the lazy validation mechanism sees it as “touched” and re-evaluates the field.
• Outcome: With this in place, the field’s required rule will be re-run and validation will clear (or show errors) as appropriate without requiring your user to manually interact with the field.

This approach lets you continue using lazy validation while automatically updating the input’s validation state when data is prefilled.