Elderform

Form handling without tears and predictable form state based on defined parameters. Elderform gives you everything you need to create robust forms and stays out of your way.

Features

• Async validation
• Create reusable forms
• Predictable form state
• Cancel form submission
• Full typescript support
• Schemaless (define your fields as you like)
• Tiny: fully packed in just ~6kb
• Use any validation library or roll your own
• Framework agnostic
• Ships with sensible defaults for form handling

• No more "how do I prevent multple submission while currently submitting"

Quick start

pnpm add xstate elderform

import * as z from 'zod';
import {createForm} from 'elderform';

const form = createForm({
  initialValues: {
    age: 10,
    name: {
      last: '',
      first: '',
      middle: '',
    },
    mother: {
      name: {
        last: '',
        first: '',
        middle: '',
      },
    },
  },
  onSubmit: () => {
    return Promise.resolve();
  },
});

form.spawn('name', null, v => zod.string().parse(v))

form.subscribe((state) => {
  ...
});

form.submit();

• Quick start
• API
• Examples

API

createForm(config)

• config (object) - config object from creating the form state machine (see below)

Config:

• initialValues? (object) - initial form values
• onSubmit(values: object) - an async function that handles form submission

Returns:

An object which provides

• submit ((...ignore?: string[]) => void) - a function to submit the form
• reset - a function to reset the form state to its initial state
• cancel (() => void) - function to cancel either the form validation or the current form submission
• submitAsync - async version of submit and resolves with the submission result
• set - ((name, value) => void) - a function to set the value for any given field
• subscribe ((stateListener) => () => void) - a state listener with the current state of the form (see below for stateListener)
• __service - the base service (xstate interpreter), made available for library authors to creating wrappers for frameworks
• validate ((field, value?) => void) - function to validate given field

• spawn ((name, value, validator) => void) - An escape hatch to spawn new fields not specified in the schema. (useful for creating dynamic forms)
• kill ((name) => void) - A function to kill a spawned field

---

State Listener

subscribe(currentState)

currentState

• state - Form State

• Boolean flags derived from form state value

  • isIdle
  • isValidating
  • isSubmitting
  • submitted
  • isError
  • isSuccess - similar to submitted

• Others

  • values (object) - form values (Defaults to an empty object)
  • data (TData | null)
    • Defaults to undefined
    • The last data returned from successfully submission
  • error (TError | null)
    • Defaults to undefined
    • The error object last from submission, if an error was thrown
  • errors (Record<string, TErrors>) - an object of errors for each field after validation
  • dataUpdatedAt (number) - The timestamp for when the form most recently submitted successfully and returned data (Defaults to 0)
  • errorUpdatedAt (number) - The timestamp for when the form most recently failed to submit successfully and returned error (Defaults to 0).

Form State

• idle - when the form isn't actively performing any operation
• validating - when the defined schema is being validated
• submitting - when the is being submitted
• submitted - if the form submitted successfully without any error
• error - if the submission attempt resulted in an error. The error is contained in the corresponding error property

Field State

• idle - when the field is not performing any action
• validating - when the field is validating
• success - if the field was validated successfully
• failed - if the field failed validation

Examples

• Basic
• Async validation