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This page introduces the basic concepts and terminology used in the @tanstack/vue-form library. Familiarizing yourself with these concepts will help you better understand and work with the library.

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Form Options

You can create options for your form so that it can be shared between multiple forms by using the formOptions function. 
const formOpts = formOptions({
  defaultValues: {
    firstName: '',
    lastName: '',
    hobbies: [],
  } as Person,
})

​
Form Instance

A Form Instance is an object that represents an individual form and provides methods and properties for working with the form. You create a form instance using the useForm composable.

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With Form Options

const form = useForm({
  ...formOpts,
  onSubmit: async ({ value }) => {
    // Do something with form data
    console.log(value)
  },
})

​
Standalone

You may also create a form instance without using formOptions: 
const form = useForm({
  onSubmit: async ({ value }) => {
    // Do something with form data
    console.log(value)
  },
  defaultValues: {
    firstName: '',
    lastName: '',
    hobbies: [],
  } as Person,
})

​
Field

A Field represents a single form input element, such as a text input or a checkbox. Fields are created using the form.Field component provided by the form instance. The component accepts a name prop and uses a scoped slot via the v-slot directive. 
<template>
  <form.Field name="fullName">
    <template v-slot="{ field }">
      <input
        :name="field.name"
        :value="field.state.value"
        @blur="field.handleBlur"
        @input="(e) => field.handleChange(e.target.value)"
      />
    </template>
  </form.Field>
</template>

​
Field State

Each field has its own state, which includes its current value, validation status, error messages, and other metadata. You can access a field’s state using the field.state property. 
const {
  value,
  meta: { errors, isValidating },
} = field.state

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Field Metadata

There are four states in the metadata that track how the user interacts with a field:
  • isTouched - Set after the user changes the field or blurs the field
  • isDirty - Set after the field’s value has been changed, even if it’s been reverted to the default (opposite of isPristine)
  • isPristine - Remains true until the user changes the field value (opposite of isDirty)
  • isBlurred - Set after the field has been blurred
const { isTouched, isDirty, isPristine, isBlurred } = field.state.meta
Field states diagram

​
Understanding ‘isDirty’

TanStack Form uses a persistent ‘dirty’ state model:
  • A field remains ‘dirty’ once changed, even if reverted to the default value
  • This is similar to Angular Form and Vue FormKit
  • Different from React Hook Form, Formik, and Final Form (which use non-persistent dirty state)
To support non-persistent dirty state, use the isDefaultValue flag: 
const { isDefaultValue, isTouched } = field.state.meta

// Re-create non-persistent dirty functionality
const nonPersistentIsDirty = !isDefaultValue
Extended field states diagram

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Field API

The Field API is an object provided by a scoped slot using the v-slot directive. This slot receives an argument named field that provides methods and properties for working with the field’s state. 
<template v-slot="{ field }">
  <input
    :name="field.name"
    :value="field.state.value"
    @blur="field.handleBlur"
    @input="(e) => field.handleChange(e.target.value)"
  />
</template>

​
Validation

@tanstack/vue-form provides both synchronous and asynchronous validation out of the box. Validation functions can be passed to the form.Field component using the validators prop. 
<template>
  <form.Field
    name="firstName"
    :validators="{
      onChange: ({ value }) =>
        !value
          ? `A first name is required`
          : value.length < 3
            ? `First name must be at least 3 characters`
            : undefined,
      onChangeAsync: async ({ value }) => {
        await new Promise((resolve) => setTimeout(resolve, 1000))
        return value.includes('error') && 'No "error" allowed in first name'
      },
    }"
  >
    <template v-slot="{ field }">
      <input
        :value="field.state.value"
        @input="(e) => field.handleChange(e.target.value)"
        @blur="field.handleBlur"
      />
      <FieldInfo :field="field" />
    </template>
  </form.Field>
</template>

​
Standard Schema Libraries

TanStack Form supports the Standard Schema specification. You can define a schema using any of these libraries:
  • Zod (v3.24.0 or higher)
  • Valibot (v1.0.0 or higher)
  • ArkType (v2.1.20 or higher)
  • Yup (v1.7.0 or higher)
<script setup lang="ts">
import { useForm } from '@tanstack/vue-form'
import { z } from 'zod'

const form = useForm({
  // ...
})

const onChangeFirstName = z.string().refine(
  async (value) => {
    await new Promise((resolve) => setTimeout(resolve, 1000))
    return !value.includes('error')
  },
  {
    message: "No 'error' allowed in first name",
  },
)
</script>

<template>
  <form.Field
    name="firstName"
    :validators="{
      onChange: z.string().min(3, 'First name must be at least 3 characters'),
      onChangeAsyncDebounceMs: 500,
      onChangeAsync: onChangeFirstName,
    }"
  >
    <template v-slot="{ field, state }">
      <label :htmlFor="field.name">First Name:</label>
      <input
        :id="field.name"
        :name="field.name"
        :value="field.state.value"
        @input="(e) => field.handleChange((e.target as HTMLInputElement).value)"
        @blur="field.handleBlur"
      />
      <FieldInfo :state="state" />
    </template>
  </form.Field>
</template>

​
Reactivity

@tanstack/vue-form offers various ways to subscribe to form and field state changes, most notably the form.useStore method and the form.Subscribe component.

​
Using useStore

<script setup lang="ts">
const firstName = form.useStore((state) => state.values.firstName)
</script>

​
Using Subscribe Component

<template>
  <form.Subscribe>
    <template v-slot="{ canSubmit, isSubmitting }">
      <button type="submit" :disabled="!canSubmit">
        {{ isSubmitting ? '...' : 'Submit' }}
      </button>
    </template>
  </form.Subscribe>
</template>
The usage of the form.useField method to achieve reactivity is discouraged since it is designed to be used thoughtfully within the form.Field component. Use form.useStore instead.

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Listeners

@tanstack/vue-form allows you to react to specific triggers and “listen” to them to dispatch side effects. 
<template>
  <form.Field
    name="country"
    :listeners="{
      onChange: ({ value }) => {
        console.log(`Country changed to: ${value}, resetting province`)
        form.setFieldValue('province', '')
      },
    }"
  >
    <template v-slot="{ field }">
      <input
        :value="field.state.value"
        @input="(e) => field.handleChange(e.target.value)"
      />
    </template>
  </form.Field>
</template>

​
Array Fields

Array fields allow you to manage a list of values within a form, such as a list of hobbies. You can create an array field using the form.Field component with the mode="array" prop. When working with array fields, you can use these methods:
  • pushValue - Add a value to the end of the array
  • removeValue - Remove a value at a specific index
  • swapValues - Swap two values at different indices
  • moveValue - Move a value from one index to another
  • insertValue - Insert a value at a specific index
  • replaceValue - Replace a value at a specific index
  • clearValues - Clear all values in the array
<template>
  <form @submit.prevent.stop="form.handleSubmit">
    <form.Field name="hobbies" mode="array">
      <template v-slot="{ field: hobbiesField }">
        <div>
          Hobbies
          <div>
            <div
              v-if="
                Array.isArray(hobbiesField.state.value) &&
                !hobbiesField.state.value.length
              "
            >
              No hobbies found.
            </div>
            <div v-else>
              <div v-for="(_, i) in hobbiesField.state.value" :key="i">
                <form.Field :name="`hobbies[${i}].name`">
                  <template v-slot="{ field }">
                    <div>
                      <label :for="field.name">Name:</label>
                      <input
                        :id="field.name"
                        :name="field.name"
                        :value="field.state.value"
                        @blur="field.handleBlur"
                        @input="(e) => field.handleChange(e.target.value)"
                      />
                      <button
                        type="button"
                        @click="hobbiesField.removeValue(i)"
                      >
                        X
                      </button>
                      <FieldInfo :field="field" />
                    </div>
                  </template>
                </form.Field>
              </div>
            </div>
            <button
              type="button"
              @click="
                hobbiesField.pushValue({
                  name: '',
                  description: '',
                  yearsOfExperience: 0,
                })
              "
            >
              Add hobby
            </button>
          </div>
        </div>
      </template>
    </form.Field>
  </form>
</template>
These are the basic concepts and terminology used in the @tanstack/vue-form library. Understanding these concepts will help you work more effectively with the library and create complex forms with ease.

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