@charlietango/use-focus-trap

useFocusTrap

Trap keyboard focus inside a DOM element, to prevent the user navigating outside a modal. When using this, make sure to combine it with a fixed position <Backdrop> that prevents the mouse from clicking input elements.

Checkout the Storybook demo.

Installation

yarn add @charlietango/use-focus-trap

API

const ref = useFocusTrap(active, options)

The useFocusTrap hook returns a ref that you should assign the the DOM element that should be root of the trap. Anything outside that element, will not be able to receive focus.

You can toggle the trap by setting the active boolean. By default it's activated once the ref is assigned.

Options

The focus trap accepts an object with these optional options, that give you a bit more control.

Name	Type	Default	Required	Description
focusSelector	string / HTMLElement	undefined	false	Assign focus when activated to the element matching this selector - or a specific element you supply. By default focus will be set to the first valid tab target.
disableAriaHider	boolean	false	false	Disables setting aria-hidden on other elements inside the document.body while the trap is active.

Example

import React from 'react'
import useFocusTrap from '@charlietango/use-focus-trap'

const Component = () => {
  const ref = useFocusTrap()
  return (
    <div ref={ref}>
      <button>Trapped to the button</button>
    </div>
  )
}

export default Component

Creating a Modal

When using this inside to create a Modal, there are a few things you need to handle:

• Trap focus
• Close on escape
• Close on backdrop clicked

BaseModal.tsx

This is the base component for creating a <Modal />. It receives an onRequestClose method, that can be triggered to tell the containing component to update it's state to close the modal. It doesn't contain a <Backdrop />, but that would be a absolute positioned component, that when clicked triggers the onRequestClose method.

import React, { useEffect } from 'react'
import ReactDOM from 'react-dom'
import useFocusTrap from '@charlietango/use-focus-trap'
import styled from 'styled-components'

type Props = {
  onRequestClose?: () => void
  children?: React.ReactNode
  isOpen: boolean
  className?: string
}

const Wrapper = styled.div`
  position: fixed;
  left: 0;
  right: 0;
  top: 0;
  bottom: 0;
  z-index: 5;
`

function BaseModal({ children, isOpen, onRequestClose, className }: Props) {
  const ref = useFocusTrap()

  function handleKeyDown(event: KeyboardEvent) {
    if (event.key === 'Escape') {
      if (onRequestClose) onRequestClose()
    }
  }

  useEffect(() => {
    if (isOpen) {
      document.addEventListener('keydown', handleKeyDown)
      return () => {
        document.removeEventListener('keydown', handleKeyDown)
      }
    }

    return
  }, [isOpen])

  const modal = (
    <Wrapper
      ref={ref}
      style={{ pointerEvents: !isOpen ? 'none' : undefined }}
      role="dialog"
      className={className}
    >
      {children}
    </Wrapper>
  )

  return ReactDOM.createPortal(modal, window.document.body)
}

BaseModal.displayName = 'BaseModal'
BaseModal.defaultProps = {}

export default BaseModal