tanstack-form

Add a validators object to form.Field with keys like onChange, onBlur, or onSubmit. Each validator returns an error message string for invalid input or undefined for valid input, and you can combine multiple timing triggers per field.

Install @tanstack/zod-form-adapter and pass zodValidator() as the validatorAdapter in useForm. Then assign Zod schemas directly to field validators, such as z.string().email() for an onChange validator.

Yes, use onChangeAsync or similar async validators and set asyncDebounceMs on the field to limit API calls. The field state exposes isValidating so you can show a loading indicator while the check runs.

Use onChangeListenTo on the dependent field to re-run validation when another field changes, then read the other value with fieldApi.form.getFieldValue inside the validator. Alternatively, use a form-level validator comparing both values.

The form's onSubmit handler must call e.preventDefault() and e.stopPropagation() before invoking form.handleSubmit(). Without preventDefault, the browser performs a native form submission and reloads the page.

Set mode="array" on the parent form.Field, then use field.pushValue, removeValue, insertValue, swapValues, and moveValue to manipulate items. Sub-fields are addressed with indexed paths like people[0].name.