如何创建自定义事件以进行上下滚动？

Question

The MDN told me how to create a custom event (which I didn't get it well)

var event = new Event('build');

// Listen for the event.
elem.addEventListener('build', function (e) { ... }, false);

// Dispatch the event.
elem.dispatchEvent(event);

and I know how to detect mouse scroll as well...

var doScroll = function (e) {
    // cross-browser wheel delta
    e = window.event || e;
    var delta = Math.max(-1, Math.min(1, (e.wheelDelta || -e.detail)));

    // Do something with `delta`
    document.body.innerHTML = delta;

    e.preventDefault();
};

if (window.addEventListener) {
    window.addEventListener("mousewheel", doScroll, false);
    window.addEventListener("DOMMouseScroll", doScroll, false);
} else {
    window.attachEvent("onmousewheel", doScroll);
}

but I don't know how to mix these two with each other and create a custom event so I can have something like this:

window.addEventListener('scrollUp', sUpFunction);
window.addEventListener('scrollDown', sDownFunction);

Thank you guys.

Answer 1

First I would use the "wheel" event instead of the non-standardrized "mousewheel" event .
I created a simple implementation of a scrollUp and scrollDown custom events dispatch.

EDIT

I have a added the IE polyfill for the CustomEvent in order to support IE as well

 // For IE support (function () { if ( typeof window.CustomEvent === "function" ) return false; //If not IE function CustomEvent ( event, params ) { params = params || { bubbles: false, cancelable: false, detail: undefined }; var evt = document.createEvent( 'CustomEvent' ); evt.initCustomEvent( event, params.bubbles, params.cancelable, params.detail ); return evt; } CustomEvent.prototype = window.Event.prototype; window.CustomEvent = CustomEvent; })(); let element = document.getElementsByClassName("scroll-area")[0], scrollUpEvent = new CustomEvent("scrollUp"), scrollDownEvent = new CustomEvent("scrollDown"); function scrollDown(){ console.log("scrolled down"); } function scrollUP(){ console.log("scrolled up"); } function scrollHappened(e){ if(e.deltaY < 0){ element.dispatchEvent(scrollUpEvent); } else { element.dispatchEvent(scrollDownEvent); } } element.addEventListener("wheel", scrollHappened); element.addEventListener("scrollUp", scrollUP); element.addEventListener("scrollDown", scrollDown); 

 .scroll-area { border: solid 2px black; height: 30px; } 

 <div class="scroll-area">Scroll on me</div>