Question

我正在使用Greasemonkey和JavaScript来修改页面。我找到了所有外部链接并在链接之前添加了图像，我想在图像上添加鼠标悬停事件。我不知道如何在循环中这样做。这就是我所拥有的：

var anchors = document.evaluate('//a[@target]',document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
var icon4 = document.createElement('img');
icon4.src = '...'; 
for (var a = 0; a < anchors.snapshotLength; a++){
  if (anchors.snapshotItem(a).href.substring(0,16) != location.href.substring(0,16)){
    icon4.addEventListener('mouseover', function(){this.title = 'Hello'}, false);
    icon4.addEventListener('mouseout', function(){this.title = ''}, false);
    anchors.snapshotItem(a).parentNode.insertBefore(icon4.cloneNode(true),anchors.snapshotItem(a));
  }
}

Answer 1

不要在这样的循环中使用匿名函数。这会导致记忆和性能问题。

无论如何，请使用the return value of insertBefore()。像这样：

var anchors = document.evaluate (
    '//a[@target]', document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null
);
var icon4   = document.createElement('img');
icon4.src   = '...';

for (var a = 0; a < anchors.snapshotLength; a++) {
    if (anchors.snapshotItem(a).href.substring(0, 16) != location.href.substring(0, 16)) {
        var newNode = anchors.snapshotItem(a).parentNode.insertBefore (
            icon4.cloneNode (true), anchors.snapshotItem (a) 
        );

        newNode.addEventListener ('mouseover', myMouseInOutHandler, false);
        newNode.addEventListener ('mouseout',  myMouseInOutHandler, false);
    }
}

function myMouseInOutHandler (zEvent) {
    if (zEvent.type == "mouseover") {
        zEvent.target.title = 'Hello';
    }
    else if (zEvent.type == "mouseout") {
        zEvent.target.title = '';
    }
}

在Greasemonkey脚本中循环添加图像和鼠标悬停事件？

1 个答案: