# Stepper

Use a stepper to increase or decrease a value, like changing the quantity from 1 to 2.

```tsx
import {
  reactExtension,
  Stepper,
} from '@shopify/ui-extensions-react/checkout';

export default reactExtension(
  'purchase.checkout.block.render',
  () => <Extension />,
);

function Extension() {
  return <Stepper label="Quantity" value={1} />;
}

```

```js
import {extension, Stepper} from '@shopify/ui-extensions/checkout';

export default extension('purchase.checkout.block.render', (root) => {
  const stepper = root.createComponent(Stepper, {
    label: 'Quantity',
    value: 1,
  });

  root.appendChild(stepper);
});

```

## StepperProps

### StepperProps

### accessibilityDescription

value: `string`

A detailed description for screen readers.

### disabled

value: `boolean`

Whether the field can be modified.

### error

value: `string`

Indicate an error to the user. The field will be given a specific stylistic treatment
to communicate problems that have to be resolved immediately.

### label

value: `string`

Content to use as the field label. This value is also used as the placeholder
when the field is empty.

### icon

value: `IconSource`

  - IconSource: 'arrowLeft' | 'arrowRight' | 'arrowUp' | 'arrowUpRight' | 'arrowDown' | 'bag' | 'calendar' | 'camera' | 'caretDown' | 'cart' | 'checkmark' | 'chevronLeft' | 'chevronRight' | 'chevronUp' | 'chevronDown' | 'clock' | 'close' | 'critical' | 'delete' | 'delivered' | 'delivery' | 'disabled' | 'discount' | 'email' | 'error' | 'errorFill' | 'external' | 'filter' | 'geolocation' | 'gift' | 'giftFill' | 'grid' | 'hamburger' | 'hollowCircle' | 'horizontalDots' | 'image' | 'info' | 'infoFill' | 'list' | 'lock' | 'magnify' | 'map' | 'marker' | 'minus' | 'mobile' | 'note' | 'orderBox' | 'pen' | 'plus' | 'profile' | 'question' | 'questionFill' | 'reorder' | 'return' | 'savings' | 'store' | 'success' | 'truck' | 'verticalDots' | 'warning' | 'warningFill'
An icon to render at the start of the field.

### id

value: `string`

A unique identifier for the field. When no `id` is set,
a globally unique value will be used instead.

### max

value: `number`

The highest decimal or integer to be accepted for the stepper field.
When used with `step` the value will round down to the max number.
Note: a buyer will still be able to use the keyboard to input a number higher than
the max. It is up to the developer to add appropriate validation.

### min

value: `number`

The lowest decimal or integer to be accepted for the stepper field.
When used with `step` the value will round up to the min number.
Note: a buyer will still be able to use the keyboard to input a number lower than
the min. It is up to the developer to add appropriate validation.

### name

value: `string`

An identifier for the field that is unique within the nearest
containing `Form` component.

### prefix

value: `string`

Text content to render before the value.

### readonly

value: `boolean`

Whether the field is read-only.

### required

value: `boolean`

Whether the field needs a value. This requirement adds semantic value
to the field, but it will not cause an error to appear automatically.
If you want to present an error when this field is empty, you can do
so with the `error` prop.

### step

value: `number`

The amount the value can increase or decrease by. This can be an integer or decimal.
If a `max` or `min` is specified with `step` when increasing/decreasing the value
via the stepper buttons the final value will always round to the `max` or `min`
rather than the closest valid amount.

### value

value: `number`

The current value for the field. If omitted, the field will be empty. You should
update this value in response to the `onChange` callback.

### onFocus

value: `() => void`

Callback when input is focused.

### onBlur

value: `() => void`

Callback when focus is removed.

### onChange

value: `(value: number) => void`

Callback when the buyer has **finished editing** a field. Unlike `onChange`
callbacks you may be familiar with from Polaris or other React component libraries,
this callback is **not** run on every change to the input. Text fields are
“partially controlled” components, which means that while the buyer edits the
field, its state is controlled by the component. Once the buyer has signalled that
they have finished editing the field (typically, by blurring the field), `onChange`
is called if the input actually changed from the most recent `value` property. At
that point, you are expected to store this “committed value” in state, and reflect
it in the text field’s `value` property.

This state management model is important given how UI Extensions are rendered. UI Extension components
run on a separate thread from the UI, so they can’t respond to input synchronously.
A pattern popularized by [controlled React components](https://reactjs.org/docs/forms.html#controlled-components)
is to have the component be the source of truth for the input `value`, and update
the `value` on every user input. The delay in responding to events from a UI
extension is only a few milliseconds, but attempting to strictly store state with
this delay can cause issues if a user types quickly, or if the buyer is using a
lower-powered device. Having the UI thread take ownership for “in progress” input,
and only synchronizing when the user is finished with a field, avoids this risk.

It can still sometimes be useful to be notified when the user makes any input in
the field. If you need this capability, you can use the `onInput` prop. However,
never use that property to create tightly controlled state for the `value`.

This callback is called with the current value of the field. If the value of a field
is the same as the current `value` prop provided to the field, the `onChange` callback
will not be run.

### onInput

value: `(value: number) => void`

Callback when the user makes any changes in the field. As noted in the documentation
for `onChange`, you **must not** use this to update `state` — use the `onChange`
callback for that purpose. Use the `onInput` prop when you need to do something
as soon as the buyer makes a change, like clearing validation errors that apply to
the field as soon as the user begins making the necessary adjustments.

This callback is called with the current value of the field.