一个细节还没有被注意到:现代桌面浏览器将不同的按钮按下视为AddEventListener的“单击”(默认为“单击”和“onclick”)。

在Chrome 42和IE11上，onclick和AddEventListener都单击左边的fire和中间的click。 在Firefox 38上，onclick只在左键点击时触发，但AddEventListener点击在左、中、右击时触发。

此外，当使用滚动游标时，中键点击行为在浏览器中非常不一致:

在Firefox上，中键单击事件总是会触发。 在Chrome浏览器上，如果中间点击打开或关闭滚动光标，它们不会触发。 在IE上，它们会在滚动光标关闭时触发，但不会在打开时触发。

同样值得注意的是，任何键盘可选择的HTML元素(如input)的“click”事件也会在元素被选中时触发空格或enter。

我想Chris Baker在一个很好的答案中总结了它，但我想添加到addEventListener()中，你也可以使用options参数，它可以让你更好地控制你的事件。例如，如果你只想运行你的事件一次，那么你可以在添加事件时使用{once: true}作为一个选项参数，只调用它一次。

    function greet() {
    console.log("Hello");
    }   
    document.querySelector("button").addEventListener('click', greet, { once: true })

上面的函数只打印“Hello”一次。 此外，如果你想清理你的事件，那么还有removeEventListener()选项。虽然使用addEventListener()有优点，但如果您的目标受众使用Internet Explorer，则此方法可能并不适用于所有情况，您仍然应该小心。你也可以在MDN上读到addEventListener，他们对如何使用它们给出了很好的解释。

简介:

addEventListener可以添加多个事件，而onclick则不能这样做。 onclick可以作为HTML属性添加，而addEventListener只能添加在<script>元素中。 addEventListener可以接受第三个参数，该参数可以停止事件传播。

两者都可用于处理事件。然而，addEventListener应该是首选的选择，因为它可以做onclick做的所有事情，甚至更多。不要使用内联onclick作为HTML属性，因为这会混淆javascript和HTML，这是一个坏的做法。它使代码更难维护。

addEventListener允许您设置多个处理程序，但在IE8或更低版本中不支持。

IE确实有attachEvent，但它并不完全相同。

如果你有另外两个函数，你可以看到区别:

var h = document.getElementById('a');
h.onclick = doThing_1;
h.onclick = doThing_2;

h.addEventListener('click', doThing_3);
h.addEventListener('click', doThing_4);

函数2、3和4可以工作，但函数1不行。这是因为addEventListener不会覆盖现有的事件处理程序，而onclick会覆盖任何现有的onclick = fn事件处理程序。

当然，另一个重要的区别是onclick总是可以工作，而addEventListener在版本9之前的ie中不能工作。你可以在IE <9中使用类似的attachEvent(语法略有不同)。

在这个回答中，我将描述定义DOM事件处理程序的三种方法。

element.addEventListener（）

代码示例:

const element = document.querySelector('a'); 元素。addEventListener('click'， event => event. preventdefault ()， true); <a href="//google.com">试着点击这个链接

addeventlistener()有多个优点:

Allows you to register unlimited events handlers and remove them with element.removeEventListener(). Has useCapture parameter, which indicates whether you'd like to handle event in its capturing or bubbling phase. See: Unable to understand useCapture attribute in addEventListener. Cares about semantics. Basically, it makes registering event handlers more explicit. For a beginner, a function call makes it obvious that something happens, whereas assigning event to some property of DOM element is at least not intuitive. Allows you to separate document structure (HTML) and logic (JavaScript). In tiny web applications it may not seem to matter, but it does matter with any bigger project. It's way much easier to maintain a project which separates structure and logic than a project which doesn't. Eliminates confusion with correct event names. Due to using inline event listeners or assigning event listeners to .onevent properties of DOM elements, lots of inexperienced JavaScript programmers thinks that the event name is for example onclick or onload. on is not a part of event name. Correct event names are click and load, and that's how event names are passed to .addEventListener(). Works in almost all browser. If you still have to support IE <= 8, you can use a polyfill from MDN.

元素。Onevent = function(){}(例如onclick, onload)

代码示例:

const element = document.querySelector('a'); 元素。onclick = event => event. preventdefault (); <a href="//google.com">试着点击这个链接

这是在DOM 0中注册事件处理程序的一种方法。现在不鼓励这样做，因为:

Allows you to register only one event handler. Also removing the assigned handler is not intuitive, because to remove event handler assigned using this method, you have to revert onevent property back to its initial state (i.e. null). Doesn't respond to errors appropriately. For example, if you by mistake assign a string to window.onload, for example: window.onload = "test";, it won't throw any errors. Your code wouldn't work and it would be really hard to find out why. .addEventListener() however, would throw error (at least in Firefox): TypeError: Argument 2 of EventTarget.addEventListener is not an object. Doesn't provide a way to choose if you want to handle event in its capturing or bubbling phase.

内联事件处理程序(onevent HTML属性)

代码示例:

<a href="//google.com" onclick="event.preventDefault();>试着点击这个链接

类似于element。Onevent，现在不鼓励了。除了那个元素的问题。Onevent有，它:

Is a potential security issue, because it makes XSS much more harmful. Nowadays websites should send proper Content-Security-Policy HTTP header to block inline scripts and allow external scripts only from trusted domains. See How does Content Security Policy work? Doesn't separate document structure and logic. If you generate your page with a server-side script, and for example you generate a hundred links, each with the same inline event handler, your code would be much longer than if the event handler was defined only once. That means the client would have to download more content, and in result your website would be slower.

另请参阅

EventTarget.addEventListener()文档(MDN) EventTarget.removeEventListener()文档(MDN) onclick vs addEventListener Dom-events标记wiki