Sam*_* Kh 2 html javascript css dom css-selectors
我试图使用Javascript更改两个表的备用行的背景颜色.
我能够使用下面的javascript来做到这一点,但我确信有一种更有效或捷径的方法来使用CSS选择器选择所需的子元素.有人可以帮忙吗？
window.onload = function() {
var elem = document.getElementsByTagName('table')
for (let c = 0; c < elem.length; c++) {
var childElem = elem[c].getElementsByTagName('tr');
for (let d = 0; d < childElem.length; d = d + 2) {
childElem[d].classList.add('alt');
}
}
}tr {
background-color: #fff;
}
.alt {
background-color: #ccc;
}<html>
<body>
<h2>Online Tx</h2>
<table>
<tr>
<td>As You Like It</td>
<td>Comedy</td>
<td></td>
</tr>
<tr>
<td>All's Well that Ends Well</td>
<td>Comedy</td>
<td>1601</td>
</tr>
<tr>
<td>Hamlet</td>
<td>Tragedy</td>
<td>1604</td>
</tr>
<tr>
<td>Macbeth</td>
<td>Tragedy</td>
<td>1606</td>
</tr>
<tr>
<td>Romeo and Juliet</td>
<td>Tragedy</td>
<td>1595</td>
</tr>
</table>
<h2>Backend tx</h2>
<table>
<tr>
<td>The Fair Youth</td>
<td>1–126</td>
</tr>
<tr>
<td>The Dark Lady</td>
<td>127–152</td>
</tr>
<tr>
<td>The Rival Poet</td>
<td>78–86</td>
</tr>
</table>
</body>
</html>你可以用纯CSS和nth-child来实现它:
tr:nth-child(2n) {
background-color: #eee;
}
tr:nth-child(2n + 1) {
background-color: #ccc;
}<h2>Online Tx</h2>
<table>
<tr>
<td>As You Like It</td>
<td>Comedy</td>
<td></td>
</tr>
<tr>
<td>All's Well that Ends Well</td>
<td>Comedy</td>
<td>1601</td>
</tr>
<tr>
<td>Hamlet</td>
<td>Tragedy</td>
<td>1604</td>
</tr>
<tr>
<td>Macbeth</td>
<td>Tragedy</td>
<td>1606</td>
</tr>
<tr>
<td>Romeo and Juliet</td>
<td>Tragedy</td>
<td>1595</td>
</tr>
</table>
<h2>Backend tx</h2>
<table>
<tr>
<td>The Fair Youth</td>
<td>1–126</td>
</tr>
<tr>
<td>The Dark Lady</td>
<td>127–152</td>
</tr>
<tr>
<td>The Rival Poet</td>
<td>78–86</td>
</tr>
</table>