event-from

Event From

Determine if a browser event was caused by mouse, touch, or key input. Can be used to:

• Ignore mouse events caused by touch input.
• Determine if focus was initiated from the keyboard (to know when to add focus styles).
• Determining if a click event was from mouse, touch, or key input.
• And anything else where knowing the type of user interaction that generated the event is helpful.
• You may also be interested in Detect It, which detects if a device is mouseOnly, touchOnly, or hybrid, and if the primary input is mouse or touch.

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Demo website (code in the demo repo)

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npm install --save event-from

import { eventFrom } from 'event-from';

const handleEvent = (event) => {
  // call eventFrom in the event handler and pass in the event
  // eventFrom will return 1 of 3 strings: 'mouse' | 'touch' | 'key'
  eventFrom(event);
};

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Ignore mouse events caused by touch input

Note that a touch interaction will fire Touch Events as the interaction is in progress (touch on the screen), and will fire Mouse Events during a long press (extended touch on the screen), or after the touch interaction has finished (after the touch is removed from the screen) to support sites that only listen for Mouse Events.

import { eventFrom } from 'event-from';

const handleMouseEvent = (e) => {
  // early return to ignore mouse events not from mouse input
  if (eventFrom(e) !== 'mouse') return;

  // code for handling mouse events from mouse input
};

element.addEventListener('mouseenter', handleMouseEvent, false);

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Determine if a focus event was from key input for accessibility

import { eventFrom } from 'event-from';

const handleFocusEvent = (e) => {
  if (eventFrom(e) === 'key') {
    // set focus styles when focus is from keyboard input
  }
};

element.addEventListener('focus', handleFocusEvent, false);

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Determine if a click event was from mouse, touch, or key input

import { eventFrom } from 'event-from';

const handleClickEvent = (e) => {
  switch (eventFrom(e)) {
    case 'mouse':
      // click event from mouse
      break;
    case 'touch':
      // click event from touch
      break;
    case 'key':
      // click event from key
      break;
  }
};

element.addEventListener('click', handleClickEvent, false);

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setEventFrom(value)

value: 'mouse' | 'touch' | 'key'

Temporarily set the return value for eventFrom(e). This is useful when manually generating events, for example calling el.focus() or el.click(), and you want eventFrom(e) to treat that event as occurring from a specific input.

import { eventFrom, setEventFrom } from 'event-from';

const handleFocusEvent = (e) => {
  if (eventFrom(e) === 'key') {
    // set focus styles when focus is from keyboard input
  }
};

const element = document.getElementById('focus-example');

element.addEventListener('focus', handleFocusEvent, false);

// some where in your code where you want to call focus on the element
// and have it be treated as an event from 'key' input
setEventFrom('key');
// now the call to eventFrom(e) in handleFocusEvent will return 'key'
element.focus();

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How it works

Event From sets passive capture phase event listeners on the document and window and tracks the recent event history to know what input type is responsible for the event that's passed to eventFrom(event).

The listeners that Event From sets are all low frequency event listeners (enter/leave/down/up/focus/etc). Event From does not set any high frequency listeners such as move or scroll listeners.