是否有一个工作周围的addEventListener回调与返回值？ [英] Is there a work around for addEventListener callbacks with return value?

问题描述

我目前正在尝试自定义（2级DOM）事件，我现在已经得到的问题， addEventListener（）不会接受返回值的回调 - 或者至少我不熟悉这个正确的方法。

I'm currently experimenting with custom (level 2 DOM) events and I've now arrived at the problem that addEventListener() will not accept callbacks that return a value -- or at least I'm unfamiliar with the proper approach to this.

基本上我想要的是：

    addEventListener("customEvent",
        function() {
            return true ;
         },
    false) ;

，因此如果我创建一个包装函数的实例 new wrapper ，

so that if I create an instance of a wrapper function new wrapper(),

     function wrapper() {
         addEventListener(...) ;
     }

这将正确返回， true 每当事件被触发和捕获。

this will properly return, true whenever the event is triggered and caught.

请记住，这是实验性的：我知道有很多解决方案，不需要从 addEventListener 方法返回。

Please keep in mind that this is experimental: I am aware that there are a plethora of solutions that do not require a return from an addEventListener method. I'm just curious whether there is a work-around or if this is in fact a dead-end and I should not bother.

感谢您的帮助！

推荐答案

AddEventListener按规范不会也不会返回值。如果addEventListener返回一个值，那么它将是无用的，因为触发callbackFunction的事件将获得返回值，而不是仅仅注册它的addEventListener。

AddEventListener by specification does not and will not return a value. If addEventListener were to return a value, it would be useless as the event that triggers the callbackFunction would get the return value and not to addEventListener which merely registered it.

addEventListener( 'onload', function() {

  // do something

  return true;

  // bool(true) would be returned to window.event[onload] and not to addEventListener if that were the case which would still make it useless to you.

}, false );

有了这个说法，有一个脏的方法，但它应该得到你想要的。 p>

With that being said, there is a dirty method but it should get you what you want.

var eventTracker = {

  retVal: false,

  retEvt: false,

  trigger: function( e ) {

    e = e || window.event;

    // some code here
  }

};

function someFn(e) {

  e = e || window.event;

  // Some code here

  eventTracker.retVal = true;

  eventTracker.retEvt = e.type;

  eventTracker.trigger.call( e );

}

// Bind the event in all browsers
if ( window.addEventListener ) {
    window.addEventListener( 'load', someFn, false );
} else if ( window.attachEvent ) {
    window.attachEvent( 'onload', someFn );
} else {
    window.onload = someFn;
}

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