在 javascript 中捕获事件
<!doctype html>
<html>
<body>
<div id = 'div' style = 'width:100px;height:100px;background:#000000;'></div>
<script type = 'text/javascript'>
document.getElementById('div').addEventListener('click',happen(),true);
function happen()
{
alert(1)
}
</script>
</body>
</html>
在上面的代码中，为什么当页面加载时会触发该事件，而当我单击 div 时不会触发该事件...另外，正确的事件名称是 click 或 onclick...
<!doctype html>
<html>
<body>
<div id = 'div' style = 'width:100px;height:100px;background:#000000;'></div>
<script type = 'text/javascript'>
document.getElementById('div').addEventListener('click',happen(),true);
function happen()
{
alert(1)
}
</script>
</body>
</html>
In the above code why the event is triggered when the page loads and not triggered when i click on the div...Also which is the correct event name click or onclick....
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评论（6）
这是因为您立即调用了该函数，并将其 null 结果传递给
addEventListener()。它应该是：
如果你想将参数传递给
happen，你必须这样写：It's because you've immediately called the function, and passed its null result to
addEventListener().It should be:
If you want to pass arguments to
happen, you'd have to write this:您立即调用该函数并将其返回值传递给
addEventListener，就像任何其他函数调用一样。取出
()。You're calling the function immediately and passing its return value to
addEventListener, just like any other function call.Take out the
().这应该有效：
This should work:
问题出在这一行：
您应该只传递函数
happen的名称，但由于添加了括号，所以您正在传递结果。试试这个：
The problem is with this line:
You should should only be passing the name of the function
happenbut since you added the parentheses, you are passing the result.Try this instead:
正如其他回答者所说，去掉（）将解决问题。
另一种方法是将函数包装在
function(){ }中，这对于 OO Javascript 来说是一个很好的实践，如下所示：document.getElementById('div').addEventListener('click ',function(){happen()},true);如果回调需要在对象内执行（在本例中不需要），这将保留范围。
As the other answerers have said, taking out the () will fix the problem.
An alternative, and a good practice for OO Javascript, is to wrap the function inside a
function(){ }, like so:document.getElementById('div').addEventListener('click',function(){happen()},true);That will retain scope if the callback needs to execute within an object (in this case it does not).
事件处理程序不需要括号
The event handler does not need parenthesis