use-simple-form

use-simple-form is a React hook for handling state in simple form applications. It supports nested object and field validation right out of the box.

Usage

import React from "react";
import useSimpleForm from "use-simple-form";

function FormComponent() {
  const [form, updateForm] = useSimpleForm({
    name: "",
    email: "",
    address: {
      street: {
        line1: "",
        line2: ""
      },
      state: "",
      zipCode: ""
    }
  });

  const zipValidator = zip => /^\d+$/.test(zip.trim());

  return (
    <form>
      <input
        name="name"
        placeholder="Name"
        value={form.name}
        onChange={updateForm()}
      />
      <input
        name="email"
        placeholder="Email Address"
        value={form.email}
        onChange={updateForm()}
      />
      <input
        name="line1"
        placeholder="Street"
        value={form.address.street.line1}
        onChange={updateForm({ parent: "address.street" })}
      />
      <input
        name="line2"
        placeholder="Apt/Unit Number"
        value={form.address.street.line2}
        onChange={updateForm({ parent: "address.street" })}
      />
      <input
        name="state"
        placeholder="State"
        value={form.address.state}
        onChange={updateForm({ parent: "address" })}
      />
      <input
        name="zipCode"
        placeholder="Zip Code"
        value={form.address.zipCode}
        onChange={updateForm({ validator: zipValidator, parent: "address" })}
      />
    </form>
  );
}

Only input's are used in this example but the hook works fine with any element that will return a value from event.target.value during onChange, like select or textarea.

API

Hook Definition

To use the hook simple give the intitial state object to the useSimpleForm hook function. Make sure you define all of the nested objects you want to use in the form in your intial state!

useSimpleForm({
  /*Initial State Object*/
});

useSimpleForm returns a 'tuple' containing the current form state in the 0th position and an updator function in the 1st position.

const [form, formUpdator] = useSimpleForm({});

Form Updator

The formUpdator is a function that returns the updator function so that you can inject configuration into the updator.

const formFieldUpdator = formUpdator({
  validator: value => {}, // Input validation function that runs before onChange
  parent: "path.to.parent.object" // Object path separated by '.' used to set nested values
});

The formUpdator function that is returned only expects the event object passed by onChange and uses event.target.name to find the field in the form state object and event.target.value to set the field in the state object. Because of this you must supply a name to your input components.

Validator

The validator expects a function that takes in the value input by the user and returns a boolean (valid = true / invalid = false). The validator then sets an addiditional value in your form state equivalent to the name + '_valid'.

// Heres an example from the usage section where we set an 'invalid' class based on this value
const zipValidator = zip => /^\d+$/.test(zip.trim());

<input
  name="zipCode"
  placeholder="Zip Code"
  value={form.address.zipCode}
  className={!form.address.zipCode_valid && 'invalid' }
  onChange={updateForm({
    validator: zipValidator,
    parent: "address"
  })}
/>;

Parent

The parent configuration variable must be a string of keys in the form state object separated by . periods.

const parent = 'x.y.z';
const obj = {
  x: {
    y: {
      z: {
        a: 'value'
      }
    }
  }
}

In this example the object defined by the parent string would be: { a: 'value' }.