Native JS 相当于 jQuery 委托 [英] Native JS equivalent to jQuery delegation

问题描述

动态创建的 dom 元素的事件委托的本机实现是什么?

What is the native implementation for event delegation on dynamically created dom elements?

我尝试查看 jQuery 源代码，但我无法遵循 .on 方法.

I tried looking at the jQuery source but I can't follow the .on method.

注意:目前我在创建 dom 元素后附加事件处理程序，这看起来很标准，但我喜欢 jQuery .on 使用这种语法处理动态创建的元素事件的方式 $(文档 ).on( "click", ".selector", handler );.

Note: Currently I attach the event handlers after the dom elements are created, which seems pretty standard but I like the way jQuery .on handles dynamically created elements events with this syntax $( document ).on( "click", ".selector", handler );.

推荐答案

发生的事情基本上是这样的:

What happens is basically this:

// $(document).on("click", <selector>, handler)
document.addEventListener("click", function(e) {
    for (var target=e.target; target && target!=this; target=target.parentNode) {
    // loop parent nodes from the target to the delegation node
        if (target.matches(<selector>)) {
            handler.call(target, e);
            break;
        }
    }
}, false);

然而，e.currentTarget 在 handler 被调用时是 document，而 e.stop[Immediate]Propagation() 会有所不同.jQuery 对此进行了大量抽象(包括调用顺序).

However, e.currentTarget is document when the handler is called, and e.stop[Immediate]Propagation() will work differently. jQuery abstracts over that (including call order) a lot.

我使用了 .matches() 方法，这还不是标准的，但已经在现代浏览器中以不同的名称提供.您可以使用自定义谓词而不是选择器来测试元素.而addEventListener显然不兼容旧的IE.

I've used the .matches() method, which is not yet standard but already available under different names in modern browsers. You might use a custom predicate to test elements instead of a selector. And addEventListener is obviously not oldIE-compatible.

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