Checkbox

A checkbox allows users to make a binary choice, i.e. a choice between one of two possible mutually exclusive options.

Features

• Tri-state checkbox. i.e. indeterminate state
• Syncs with disabled state of fieldset
• Syncs with form reset events
• Can be toggled programmatically

Installation

To use the checkbox machine in your project, run the following command in your command line:

npm install @zag-js/checkbox @zag-js/react
# or
yarn add @zag-js/checkbox @zag-js/react

npm install @zag-js/checkbox @zag-js/vue
# or
yarn add @zag-js/checkbox @zag-js/vue

npm install @zag-js/checkbox @zag-js/vue
# or
yarn add @zag-js/checkbox @zag-js/vue

npm install @zag-js/checkbox @zag-js/solid
# or
yarn add @zag-js/checkbox @zag-js/solid

This command will install the framework agnostic checkbox logic and the reactive utilities for your framework of choice.

Anatomy

To set up the checkbox correctly, you'll need to understand its anatomy and how we name its parts.

Each part includes a data-part attribute to help identify them in the DOM.

On a high level, the checkbox consists of:

• Root: The root container for the checkbox
• Label: The label that gives the user information on the checkbox
• Control: The element that visually represents the checkbox.
• Hidden Input: The hidden input that holds the value of the checkbox. Used within forms.

Usage

First, import the checkbox package into your project

import * as checkbox from "@zag-js/checkbox"

The checkbox package exports two key functions:

• machine — The state machine logic for the checkbox widget.
• connect — The function that translates the machine's state to JSX attributes and event handlers.

Next, import the required hooks and functions for your framework and use the checkbox machine in your project 🔥

import * as checkbox from "@zag-js/checkbox"
import { useMachine, normalizeProps } from "@zag-js/react"

function Checkbox() {
  const [state, send] = useMachine(checkbox.machine({ id: "1" }))

  const api = checkbox.connect(state, send, normalizeProps)

  return (
    <label {...api.rootProps}>
      <span {...api.labelProps}>
        Input is {api.isChecked ? "checked" : "unchecked"}
      </span>
      <div {...api.controlProps} />
      <input {...api.hiddenInputProps} />
    </label>
  )
}

import * as checkbox from "@zag-js/checkbox"
import { normalizeProps, useMachine } from "@zag-js/vue"
import { defineComponent, h, Fragment, computed } from "vue"

export default defineComponent({
  name: "Checkbox",
  setup() {
    const [state, send] = useMachine(checkbox.machine({ id: "checkbox" }))

    const apiRef = computed(() =>
      checkbox.connect(state.value, send, normalizeProps),
    )

    return () => {
      const api = apiRef.value
      return (
        <label {...api.rootProps}>
          <span {...api.labelProps}>
            Input is {api.isChecked ? "checked" : "unchecked"}
          </span>
          <div {...api.controlProps} />
          <input {...api.hiddenInputProps} />
        </label>
      )
    }
  },
})

<script setup>
  import * as checkbox from "@zag-js/checkbox"
  import { normalizeProps, useMachine } from "@zag-js/vue"
  import { computed } from "vue"

  const [state, send] = useMachine(checkbox.machine({ id: "1" }))

  const api = computed(() =>
    checkbox.connect(state.value, send, normalizeProps),
  )
</script>

<template>
  <label v-bind="api.rootProps">
    <span v-bind="api.labelProps">
      Input is
      <span v-if="api.isChecked"> checked</span>
      <span v-else> unchecked</span>
    </span>
    <div v-bind="api.controlProps" />
    <input v-bind="api.hiddenInputProps" />
  </label>
</template>

import * as checkbox from "@zag-js/checkbox"
import { normalizeProps, useMachine } from "@zag-js/solid"
import { createMemo, createUniqueId } from "solid-js"

function Checkbox() {
  const [state, send] = useMachine(checkbox.machine({ id: createUniqueId() }))

  const api = createMemo(() => checkbox.connect(state, send, normalizeProps))

  return (
    <label {...api().rootProps}>
      <span {...api().labelProps}>
        Input is {api().isChecked ? "checked" : "unchecked"}
      </span>
      <div {...api().controlProps} />
      <input {...api().hiddenInputProps} />
    </label>
  )
}

Indeterminate checkboxes

To make a checkbox indeterminate, set the context's indeterminate property to true

const [state, send] = useMachine(
  checkbox.machine({
    indeterminate: true,
  }),
)

Disabling the checkbox

To make a checkbox disabled, set the context's disabled property to true

const [state, send] = useMachine(
  checkbox.machine({
    disabled: true,
  }),
)

Making it checked by default

To make a checkbox checked by default, set the context's checked property to true

const [state, send] = useMachine(
  checkbox.machine({
    checked: true,
  }),
)

Listening for changes

When the checkbox value changes, the onChange callback is invoked.

const [state, send] = useMachine(
  checkbox.machine({
    onChange({ checked }) {
      console.log("checkbox is:", checked)
      // 'checked' | 'unchecked' | 'indeterminate'
    },
  }),
)

Usage within forms

To use checkbox within forms, use the exposed hiddenInputProps from the connect function and ensure you pass name value to the machine's context. It will render a hidden input and ensure the value changes get propagated to the form correctly.

const [state, send] = useMachine(
  checkbox.machine({
    name: "fruits",
  }),
)

Styling guide

Earlier, we mentioned that each checkbox part has a data-part attribute added to them to select and style them in the DOM.

Checked state

When the checkbox input is checked, the data-checked attribute is added to the root, control and label parts.

[data-part="root"][data-state="checked|unchecked|indeterminate"] {
  /* styles for when checkbox is checked */
}

[data-part="control"][data-state="checked|unchecked|indeterminate"] {
  /* styles for when checkbox is checked */
}

[data-part="label"][data-state="checked|unchecked|indeterminate"] {
  /* styles for when checkbox is checked */
}

Focused State

When the checkbox input is focused, the data-focus attribute is added to the root, control and label parts.

[data-part="root"][data-focus] {
  /* styles for root focus state */
}

[data-part="control"][data-focus] {
  /* styles for control focus state */
}

[data-part="label"][data-focus] {
  /* styles for label focus state */
}

Disabled State

When the checkbox is disabled, the data-disabled attribute is added to the root, control and label parts.

[data-part="root"][data-disabled] {
  /* styles for root disabled state */
}

[data-part="control"][data-disabled] {
  /* styles for control disabled state */
}

[data-part="label"][data-disabled] {
  /* styles for label disabled state */
}

Invalid State

When the checkbox is invalid, the data-invalid attribute is added to the root, control and label parts.

[data-part="root"][data-invalid] {
  /* styles for root invalid state */
}

[data-part="control"][data-invalid] {
  /* styles for control invalid state */
}

[data-part="label"][data-invalid] {
  /* styles for label invalid state */
}

Methods and Properties

The checkbox's api provides properties and methods:

• isCheckedbooleanWhether the checkbox is checked
• isDisabledbooleanWhether the checkbox is disabled
• isIndeterminatebooleanWhether the checkbox is indeterminate
• isFocusedbooleanWhether the checkbox is focused
• checkedStateCheckedStateThe checked state of the checkbox
• setChecked(checked: CheckedState) => voidFunction to set the checked state of the checkbox
• toggleChecked() => voidFunction to toggle the checked state of the checkbox