关于javascript：window.onload / onunload与body.onload / onunload之间的区别

Differences between window.onload/onunload and body.onload/onunload

我已经阅读了问题window.onload vs

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<!DOCTYPE html PUBLIC"-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
test 1

<script type="text/javascript">

var initialSelectedIndex = 0;

function resetMenu()
{
document.getElementById("fruitMenu").selectedIndex = initialSelectedIndex;
}

</head>
<body onloadx="resetMenu();" onunload="resetMenu();">
<br />
<select id="fruitMenu">
<option value ="apple">apple</option>
<option value ="banana">banana</option>
<option value ="strawberry">strawberry</option>
<option value ="grape">grape</option>
</select>

<p>
google

</p>

</body>
</html>

和：

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<!DOCTYPE html PUBLIC"-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
test 2

<script type="text/javascript">

var initialSelectedIndex = 0;

function resetMenu()
{
document.getElementById("fruitMenu").selectedIndex = initialSelectedIndex;
}

window.onload = resetMenu();
window.onunload = resetMenu();

</head>
<body>
<br />
<select id="fruitMenu">
<option value ="apple">apple</option>
<option value ="banana">banana</option>
<option value ="strawberry">strawberry</option>
<option value ="grape">grape</option>
</select>

<p>
google

</p>

</body>
</html>

在"测试1"页面上，如果您从下拉菜单中选择一个项目，然后单击链接以离开该页面，然后单击"后退"按钮，则菜单将重置为其初始状态。不过，"测试2"页面不会发生这种情况。为什么？

虽然这是一个测试，但我的目标是使用RegisterStartupScript或RegisterClientScriptBlock在aspx页面上执行类似的操作，因此我希望能够不使用主体onload / onunload但使用window.onload / onunload来重新创建"测试1"的行为。。