Code Reading - Shared React Form Library

Published on Thursday, January 12, 2017

Presenter: Seiji


React is not an opionated library

  • too many options for building forms
  • we ended up with a bunch of different implementations / approaches

Forms are omnipresent in our app

  • lots of repeated code
  • need to DRY this up


  • Build out library to manage form state + validation + submission
  • Build reusable form component specific to our domain


  • Reviewed all our current approaches
  • Melded into single, shareable component

Shared Component Library

Can be used for controlled + uncontrolled inputs

  • examples at /admin/react/forms
  • documentation on ironboard wiki

Robust test coverage

Default styles can be overridden

Acts as building block / starting point for new form

  • won’t just magically build your entire form for you
  • use lego blocks to build lego set

Alt Form: existing library, but outdated and not super functional, so Seiji rebuilt one specific to our app

Uses Curring pattern

  • Referred to in React community as “high order component”

3 Objects:

  1. Form Object
  2. Form Component
  3. Form Connector
Form Object      Form Component
     \                 /
      \               /
        Form Connector
        React Form


Goal: build form with first name, last name submittable inputs

Walkthrough (propriety code omitted)

  1. Create FormComponent
    • updates UI on state changes
    • holds Input and Button components
  2. Build FormObject
    • stores field configuration
    • underlying implementation: AltStore
    • dispatch actions through Alt dispatcher
    • uses global Alt instance to dispatch events, so will need to namespace events
    • object that’ll have field names (keys)
    • values are the validation functions
    • to declare something invalid, throw an Error
  3. Import FormConnector
    • connector syncs FormObject and FormComponent states
    • render ConnectedForm into DOM
    • connector gives us lotsa good props to use
    • passes FormObject into FormComponent, returns React component w/ everything needed to render
  4. Import individual input components from shared react components (ex. TextFieldInput, etc)
    • Use REST spread syntax to pass fields into props:
// generic example
var props = {
  a: 'hello',
  b: 'world'
var {a,} = props

// input component example
const {fields} = this.props

  labelText='Cool label'
  1. Question: how to validate server-side?
    • might need more configuration, but FormObject does handle onFormSubmitFailure
  2. Sending data to server
    • configure onSubmit function on FormObject
    • takes in current form state
    • that function makes a POST request to whatever endpoint


Bit of a learning curve, but should help standardize our forms.

Handles decision making for you

Abstracts out state management

Goal: open source this project

  • good resource for Alt users
  • nothing else out there as good as ReactForms