@ginger.io/react-use-form
v0.5.7
Published
React `useForm` is a custom [hook](https://reactjs.org/docs/hooks-intro.html) that makes building forms easier in React.
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React useForm
React useForm
is a custom hook that makes building forms easier in React.
In React, you often need to extract form data and map it to the shape that your backend API expects -- e.g. a graphQL type. This can quickly get complicated when your object contains nested types (e.g. person.address.street
). The useForm
hook makes this easy.
Just specify your object's shape + validation rules and useForm
gives you a fields
object with properties that recursively mirror your object (e.g. person.address.street.value
, person.address.street.error
, person.address.street.setValue
etc). You bind those to input components of your choice (e.g. <TextField field={person.address.street} />
) Then, when the user clicks your "submit" button, simply call getValue()
to get your fully-formed object out -- no manual data mapping required.
Installation
npm install @ginger.io/react-use-form
Usage
import React from 'react'
import { useForm, stringField, field, Field } from "@ginger.io/react-use-form"
type Person = {
name: string
phone: string
address: Address
}
type Address = {
street: string
zip: number
}
function PersonForm(props: {}) {
const { fields, validate, getValue } = useForm<Person>({
name: stringField(),
phone: stringField()
address: {
street: stringField(),
zip: field({
rules: [
zip => (zip.toString().length === 5 ? undefined : 'Invalid zip code')
]
})
}
})
const onSubmit = async () => {
if (await validate()) { // trigger validation
console.log(getValue()) // get your fully-formed Person
}
}
return (
<>
<TextField label="Name" field={fields.name} />
<TextField label="Phone" field={fields.phone} />
<TextField label="Street" field={fields.address.street} />
<NumberField label="Zip" field={fields.address.zip} />
<button onClick={onSubmit} />
</>
)
}
function TextField(props: { label: string; field: Field<string> }) {
const { label, field } = props
return (
<>
<label>{label}</label>
<input
type="text"
value={field.value}
onChange={e => field.setValue(e.target.value)}
/>
<p>{field.error}</p>
</>
)
}
function NumberField(props: { label: string; field: Field<number> }) {
const { label, field } = props
return (
<>
<label>{label}</label>
<input
type="number"
value={field.value}
onChange={e => field.setValue(parseInt(e.target.value))}
/>
<p>{field.error}</p>
</>
)
}
Hook API
type UseForm<T> = {
fields: Fields<T> // field bindings
validate: () => boolean // trigger validation
getValue: () => T // retrieve the current form value
isEmpty: boolean // true if all fields are undefined, null or ""
isTouched: boolean // true if any of the field-level `touched` is true
reset: () => void // reset form to initial state
}
function useForm<T>(fieldDefinitions: FieldDefinitions<T>, defaultValue?: T, onStateChange?: (value: T) => void): UseForm<T>
fields: Fields
A recursive mirror of your object, where each field is a Field<T>
.
validate: () => Promise
Triggers the validation rules for all properties (use this if you want validation errors to show up after the user clicks your submit button vs right away with fields.foo.validate
).
getValue: () => T
Returns your fully formed object. Make sure it's valid first either by disabling your submit button when fields have errors or calling validate()
, before trying to use it.
isEmpty: boolean
This value is true
if all fields of T
are either: undefined | null | "" | [] (empty array)
, false
otherwise. And this value is kept up to date across renders.
isTouched: boolean
This value is true
if at least of one field-level touched
value is true
.
reset: () => void
Reset all fields to their initial state.
Field API
A Field<T>
represents the state for a specific field on your object, with the following properties:
value: T
The current value of this property (changes across renders)
setValue(input: T, options?: { runValidation: boolean }) => Promise | void
The setValue
handler for this property. Passing a new value triggers a re-render of your form. Normally this function returns void
.
But if you want to update your field value and run validation at the same time, you can pass { runValidation: true }
. And, when you do the TS type signature will automatically change to Promise<boolean>
, which you can use to determine if your field passed validation or not.
error: string | undefined
The first error triggered by your validation rules or undefined
validate: () => void
The validate
handler for this property. Calling this triggers the validation rules for this property and triggers a re-render.
Default Values
There are two ways to specify a default value:
Pass a fully formed
T
as the second parameter touseForm
, e.g.useForm({...}, defaultValue)
. This is useful when you have an existing object from your API and you want to "edit" it in your form.Pass a default value for a specific field, using the
field
helper method -- e.g:
useForm({
name: field({ default: "foo" })
})
Note: If you pass a fully formed object to seed your form values, those object's values will supersede any field-level default values you've specified. This is desireable for the intended usecase of loading a pre-existing entity/draft into your form.
Field helper functions
React useForm provides a handful of convenience methods to construct fields for common default values:
field()
A generic field whose default value is undefined
(unless overridden by passing the default:
parameter shown in the previous section). For cases where you want a default value that is not undefined
, see the other helper methods below (or just pass the default:
option).
stringField()
A string field whose default value is ""
.
React input components often expect their "empty" state to be the empty string instead of undefined
. In those cases, you'll want to use this helper over the more generic field()
helper.
booleanField()
A boolean field whose default value is false
.
numberField()
A number field whose default value is 0
.
positiveNumberField()
A number field whose default value is 1
and requires positive numbers.
nonNegativeNumberField()
A number field whose default value is 0
and requires non-negative numbers (0 and higher).
arrayField()
An array field whose default value is []
.
nonEmptyArrayField()
An array field whose default value is []
, but has a validation rule attached that shows an error if the array is empty when validation on this field is triggered.