1、每个子input标签都需要进行判断
2、使用开闭原则，一旦满足条件就改变默认值
3、在给主input标签注册事件时，要求主input标签的checked值赋值给子标签
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
* {
padding: 0;
margin: 0;
}
.wrap {
300px;
margin: 100px auto 0;
}
table {
border-collapse: collapse;
border-spacing: 0;
border: 1px solid #c0c0c0;
300px;
}
th,
td {
border: 1px solid #d0d0d0;
color: #404060;
padding: 10px;
}
th {
background-color: #09c;
font: bold 16px "微软雅黑";
color: #fff;
}
td {
font: 14px "微软雅黑";
}
tbody tr {
background-color: #f0f0f0;
}
tbody tr:hover {
cursor: pointer;
background-color: #fafafa;
}
</style>
</head>
<body>
<div class="wrap">
<table>
<thead>
<tr>
<th>
<input type="checkbox" id="theadInp" />
</th>
<th>菜名</th>
<th>饭店</th>
</tr>
</thead>
<tbody id="tbody">
<tr>
<td>
<input type="checkbox" />
</td>
<td>地三鲜</td>
<td>田老师</td>
</tr>
<tr>
<td>
<input type="checkbox" />
</td>
<td>西红柿鸡蛋</td>
<td>田老师</td>
</tr>
<tr>
<td>
<input type="checkbox" />
</td>
<td>醋溜土豆丝</td>
<td>田老师</td>
</tr>
<tr>
<td>
<input type="checkbox" />
</td>
<td>萝卜干炒黄豆儿</td>
<td>田老师</td>
</tr>
</tbody>
</table>
</div>
<script>
var inp = document.getElementById("theadInp");
var tbody = document.getElementById("tbody");
var inps = tbody.getElementsByTagName("input");
//给表头的input标签注册事件
inp.onclick = function () {
for (var i = 0; i < inps.length; i++) {
inps[i].checked = this.checked;
}
}
//给tbody中的input标签注册事件
for (var i = 0; i < inps.length; i++) {
inps[i].onclick = function () {
var bool = true;
for (var i = 0; i < inps.length; i++) {
if (inps[i].checked === false) {
bool = false;
}
}
inp.checked = bool;
}
}
</script>
</body>
</html>
