subscribe-ui-event
With subscribe-ui-event
, instead of calling multiple window.addEventListener('scroll', eventHandler);
by different components, call subscribe('scroll', eventHandler)
. It will only add single event listener and dispatch event to those who subscribe the event via eventemitter3.
Why single event? More performance and less memory consumption.
Single Event Listener v.s. Multiple Event Listeners
The jsperf runs 10 addEventListener
and 10 non-throttling subscribe
, and the outcome is that the ops/sec of subscribe
is slightly less. But in regular case, you will use throttling subscribe
, and it will be more performant.
For 10 addEventListener
, the difference of memory consumption between peak and trough is about 4.1K.
For 10 subscribe
, the difference of memory consumption between peak and trough is about 1.0K.
Other Benifits
- Do throttling by default.
- Get
document.body.scrollTop
,window.innerWidth
once. - Provide
requestAnimationFrame
throttle for the need of high performance. - Be able to use like
scrollStart
(see below) those edge events.
Install
npm install subscribe-ui-event
API
subscribe
Subscription
Provide throttled version of window or document events, such like scroll
, resize
, touch
and visibilitychange
to subscribe, see below.
Note on IE8 or the below, the throttle will be turned off because the event object is global and will be deleted for setTimeout or rAF.
Example:
; { // e is the native event object and // payload is the additional information ...}// 50ms throttle by defaultconst subscription = ;// remove latersubscription;
Addtional Payload
The format of the payload is:
type: <String> // could be 'scroll', 'resize' ... // you need to pass options.enableScrollInfo = true to subscribe to get the following data scroll: top: <Number> // The scroll position, i.g., document.body.scrollTop delta: <Number> // The delta of scroll position, it is helpful for scroll direction // you need to pass options.enableResizeInfo = true to subscribe to get the following data resize: width: <Number> // The client width height: <Number> // The client height // you need to pass options.enableTouchInfo = true to subscribe to get the following data touch: axisIntention: <String> // 'x', 'y', or ''. startX: <Number> startY: <Number> deltaX: <Number> deltaY: <Number>
Options
options.throttleRate
allows of changing the throttle rate, and the default value is 50 (ms). Set 0 for no throttle. On IE8, there will be no throttle, because throttling will use setTimeout or rAF to achieve, and the event object passed into event handler will be overwritten.
options.context
allows of setting the caller of callback function.
options.useRAF = true
allows of using requestAnimationFrame
instead of setTimeout
.
options.enableScrollInfo = true
allows of getting scrollTop
.
options.enableResizeInfo = true
allows of getting width
and height
of client.
options.enableTouchInfo = true
allows of getting touch information (see above).
eventType
could be one of the following:
- scroll - window.scoll
- scrollStart - The start of window.scoll
- scrollEnd - The end of window.scoll
- resize - window.resize
- resizeStart - The start window.resize
- resizeEnd - The end window.resize
- visibilitychange - document.visibilitychange (IE8 doesn't support)
- touchmoveStart - The start of window.touchmove
- touchmoveEnd - The end of window.touchmove
- touchmove - window.touchmove
- touchstart - window.touchstart
- touchend - window.touchend
options.eventOptions
: An options object that specifies characteristics about the event listener (if passive event is supported by the browser)
unsubscribe
Void
Unsubscribe an event listener, suggest to use subscription.unsubscribe()
, because it may accidentally unsubscribe those events having the same eventType
and callback
but different throttleRate
.
Credits
- This library runs full browser test suite using Sauce Labs.
License
This software is free to use under the BSD license. See the LICENSE file for license text and copyright information.