Question

直到今天我才弄清楚事件传播是如何运作的，并且在我现有的代码库中进行了大量的测试，但是arghhhhhhhh该死的javascript ......对你来说似乎没什么好看的：X

这是我的问题，我在锚上定义了一组事件：

theLink.setAttribute('onMouseOver','doSomething(this)');    **// works**

theLink.addEventListener("mouseout", function(event){doSomethingElse(event)}, false);  **// does not work**

theLink.onmouseout = function(event){doSomethingElse(event)};     **// does not work**

只有我在第一个例子中定义事件时，它似乎也在第二个或第三个定义中工作。但我无法使用该定义，因为我必须传递事件对象。

任何提示？我正在使用firefox。

Answer 1

所有这三个都使用以下代码（在Firefox中）为我工作：

HTML：

<a id="link1">Link 1</a>
<a id="link2">Link 2</a>
<a id="link3">Link 3</a>

JS：

var link1 = document.getElementById("link1");
var link2 = document.getElementById("link2");
var link3 = document.getElementById("link3");

window.doSomething = function(event) {
    console.log(event);
}

link1.setAttribute('onMouseOver', 'doSomething(this)');

link2.addEventListener("mouseout", function(event) {
    doSomething(event)
}, false);

link3.onmouseout = function(event) {
    doSomething(event)
};

这是一个有效的jsfiddle：http://jsfiddle.net/magicaj/qk6wU/

您也可以考虑使用像jQuery这样的库来处理与某些版本的IE不支持的addEventListener方法的跨浏览器不兼容，JS看起来像这样：

$("#link1").mouseover(doSomething);
$("#link2").mouseover(doSomething);
$("#link3").mouseover(doSomething);

Answer 2

包含跨浏览器的答案

function doSomething( event ) {
    if( console && console.log ) {
        console.log( this );
        console.log( event );
    }
    else {
        alert( this === window ? 'WINDOW' : this.tagName );
        alert( event );
    }
}


var link1 = document.getElementById("link1");
var link2 = document.getElementById("link2");
var link3 = document.getElementById("link3");

// `this` within your handler will be `window` and not the link
link1.setAttribute( 'onMouseOver', 'doSomething( event )' ); 

// to attach event listeners you have to do a bit more work
// ( best to make a function rather than doing this each time
if( document.addEventListener ) {
    // compliant browsers
    link2.addEventListener('mouseover', doSomething, false);
} else {
    // internet explorer
    link2.attachEvent( 'onmouseover', function() {
        // grab the event object from the window
        var e = window.event;
        // normalise it a bit i.e. make it a bit more like a compliant browsers event object
        e.target = e.srcElement;
        e.preventDefault = function(){ e.returnValue = false };
        e.stopPropagation = function(){ e.cancelBubble = true };
        // and forward to your handler making sure that `this` is properly set
        doSomething.call( this, e );
    });
}

link3.onclick = doSomething;

注意避免将处理程序包装在不必要的匿名函数中，这会浪费你的力量而你会丢失处理程序中的this 所以而不是

link3.onclick = function( event ) { doSomething( event ) };

直接分配处理程序

link3.onclick = doSomething;

Javascript事件处理有问题

2 个答案: