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HomeWeb Front-endH5 Tutorialonclick = xxx这种赋值写法绑定事件的原理是什么?

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合理猜测:给onclick赋值的内部操作时,remove掉原来的,add上新的。 路过
不同浏览器不一定是这个结果
底层代码肯定不是JS

仅趴了机器上几年前最老的blink代码看了下
EventListenerMap 里靠的是 EventListenerVector
这玩意就是个 Vector
typedef Vector
这么搞的

onclick setting 时候是 vector->find 后没有对应 handle
再 append 进去的
再次 setting 时是 find 有
就先 remove 老的再 append
没见 Vector 有用到(定义过) replace 方法

所以(在这么实现的浏览器上)才有这种现象

最终还是轮子哥猜对了。 这个ff和chrome/safari行为是不一致的(edge未测试)。按照现在的规范(html.spec.whatwg.org/mu),blink/webkit的行为是错误的。



嗯,恭喜轮子猜对了一个错误的实现。 js就是猜的人多,而不去看源码或规范,所以有一堆误导大众的文章 订阅者模式,内部应该是通过一个列表来维护事件响应的,所以每次为OnClick赋值的时候会替换原来的事件委托。 你这是毛病得改,对未在需求文档中定义的行为不要妄加猜测,因为说不定哪天就改了呢。

这个可能是listener和onclick一个是列表,一个是属性,属性赋值自然覆盖。先执行属性,再执行监听器列表。

当然也可以有其它和实现,那表现就不一样了,你依赖这种调用顺序是错误的,我完全可以所有listener并发,符合需求,却让你的程序出bug,你这就是作死,不要学习那些上古遗留的糟粕 属性,setter方法,去掉旧的,加上新的……你懂了吧,我猜的 跟所谓的主线程队列里面加入子线程是不是一个道理(疑惑 轮子哥猜中了。就是队列,出了重新进,就从队尾到队头了
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