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on.js
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on.js
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import { debounce } from './debounce'
import { throttle } from './throttle'
export default function on (el, event, modifiers, callback) {
let listenerTarget = el
let handler = e => callback(e)
let options = {}
// This little helper allows us to add functionality to the listener's
// handler more flexibly in a "middleware" style.
let wrapHandler = (callback, wrapper) => (e) => wrapper(callback, e)
if (modifiers.includes("dot")) event = dotSyntax(event)
if (modifiers.includes('camel')) event = camelCase(event)
if (modifiers.includes('passive')) options.passive = true
if (modifiers.includes('capture')) options.capture = true
if (modifiers.includes('window')) listenerTarget = window
if (modifiers.includes('document')) listenerTarget = document
if (modifiers.includes('prevent')) handler = wrapHandler(handler, (next, e) => { e.preventDefault(); next(e) })
if (modifiers.includes('stop')) handler = wrapHandler(handler, (next, e) => { e.stopPropagation(); next(e) })
if (modifiers.includes('self')) handler = wrapHandler(handler, (next, e) => { e.target === el && next(e) })
if (modifiers.includes('away') || modifiers.includes('outside')) {
listenerTarget = document
handler = wrapHandler(handler, (next, e) => {
if (el.contains(e.target)) return
if (el.offsetWidth < 1 && el.offsetHeight < 1) return
// Additional check for special implementations like x-collapse
// where the element doesn't have display: none
if (el._x_isShown === false) return
next(e)
})
}
if (modifiers.includes('once')) {
handler = wrapHandler(handler, (next, e) => {
next(e)
listenerTarget.removeEventListener(event, handler, options)
})
}
// Handle :keydown and :keyup listeners.
handler = wrapHandler(handler, (next, e) => {
if (isKeyEvent(event)) {
if (isListeningForASpecificKeyThatHasntBeenPressed(e, modifiers)) {
return
}
}
next(e)
})
if (modifiers.includes('debounce')) {
let nextModifier = modifiers[modifiers.indexOf('debounce')+1] || 'invalid-wait'
let wait = isNumeric(nextModifier.split('ms')[0]) ? Number(nextModifier.split('ms')[0]) : 250
handler = debounce(handler, wait)
}
if (modifiers.includes('throttle')) {
let nextModifier = modifiers[modifiers.indexOf('throttle')+1] || 'invalid-wait'
let wait = isNumeric(nextModifier.split('ms')[0]) ? Number(nextModifier.split('ms')[0]) : 250
handler = throttle(handler, wait)
}
listenerTarget.addEventListener(event, handler, options)
return () => {
listenerTarget.removeEventListener(event, handler, options)
}
}
function dotSyntax(subject) {
return subject.replace(/-/g, ".")
}
function camelCase(subject) {
return subject.toLowerCase().replace(/-(\w)/g, (match, char) => char.toUpperCase())
}
function isNumeric(subject){
return ! Array.isArray(subject) && ! isNaN(subject)
}
function kebabCase(subject) {
return subject.replace(/([a-z])([A-Z])/g, '$1-$2').replace(/[_\s]/, '-').toLowerCase()
}
function isKeyEvent(event) {
return ['keydown', 'keyup'].includes(event)
}
function isListeningForASpecificKeyThatHasntBeenPressed(e, modifiers) {
let keyModifiers = modifiers.filter(i => {
return ! ['window', 'document', 'prevent', 'stop', 'once'].includes(i)
})
if (keyModifiers.includes('debounce')) {
let debounceIndex = keyModifiers.indexOf('debounce')
keyModifiers.splice(debounceIndex, isNumeric((keyModifiers[debounceIndex+1] || 'invalid-wait').split('ms')[0]) ? 2 : 1)
}
// If no modifier is specified, we'll call it a press.
if (keyModifiers.length === 0) return false
// If one is passed, AND it matches the key pressed, we'll call it a press.
if (keyModifiers.length === 1 && keyToModifiers(e.key).includes(keyModifiers[0])) return false
// The user is listening for key combinations.
const systemKeyModifiers = ['ctrl', 'shift', 'alt', 'meta', 'cmd', 'super']
const selectedSystemKeyModifiers = systemKeyModifiers.filter(modifier => keyModifiers.includes(modifier))
keyModifiers = keyModifiers.filter(i => ! selectedSystemKeyModifiers.includes(i))
if (selectedSystemKeyModifiers.length > 0) {
const activelyPressedKeyModifiers = selectedSystemKeyModifiers.filter(modifier => {
// Alias "cmd" and "super" to "meta"
if (modifier === 'cmd' || modifier === 'super') modifier = 'meta'
return e[`${modifier}Key`]
})
// If all the modifiers selected are pressed, ...
if (activelyPressedKeyModifiers.length === selectedSystemKeyModifiers.length) {
// AND the remaining key is pressed as well. It's a press.
if (keyToModifiers(e.key).includes(keyModifiers[0])) return false
}
}
// We'll call it NOT a valid keypress.
return true
}
function keyToModifiers(key) {
if (! key) return []
key = kebabCase(key)
let modifierToKeyMap = {
'ctrl': 'control',
'slash': '/',
'space': '-',
'spacebar': '-',
'cmd': 'meta',
'esc': 'escape',
'up': 'arrow-up',
'down': 'arrow-down',
'left': 'arrow-left',
'right': 'arrow-right',
'period': '.',
'equal': '=',
}
modifierToKeyMap[key] = key
return Object.keys(modifierToKeyMap).map(modifier => {
if (modifierToKeyMap[modifier] === key) return modifier
}).filter(modifier => modifier)
}