javascript 如何使用 jQuery 或 JS 检查事件处理程序是否存在？
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How to check if an event handler exist using jQuery or JS?
提问by Omar Abid
I want to check if an event is available or not before binding a function to it. The problem is that Google Chrome support the event "loadedmetadata" in the Video element while FireFox don't.
我想在绑定函数之前检查事件是否可用。问题是 Google Chrome 支持 Video 元素中的事件“loadedmetadata”，而 FireFox 不支持。
I did the following
我做了以下
$('video').bind('loadedmetadata', videoloaded);
videoloaded();
It worked well in Firefox but when I tried in Chrome, the function was executed twice (which is logical). I want to check if loadedmetadataevent handler exists or not to run the function only one time in each browser.
它在 Firefox 中运行良好，但是当我在 Chrome 中尝试时，该函数执行了两次（这是合乎逻辑的）。我想检查loadedmetadata事件处理程序是否存在，以便在每个浏览器中只运行一次该函数。
If such possibility doesn't exist, any intelligent work around for this?
如果这种可能性不存在，是否有任何智能解决方法？
采纳答案by BrunoLM
Check the $video.data("events")if this object contains your event, since you are using .bindall events of this element will be stored in this object.
检查$video.data("events")此对象是否包含您的事件，因为您正在使用.bind此元素的所有事件都将存储在此对象中。
var $video = $("#video");
var $ve = $video.data("events");
// checking if a `loadedmetadata` object exists in `data("events")`
if ($ve != null && typeof($ve.loadedmetadata) !== undefined)
{
// has loadedmetadata event
}
Full working example on jsFiddle
jsFiddle 上的完整工作示例
