<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title> </title>
</head>
<body>
<table>
<thead>
<tr>
<th>
<input type="checkbox" id="j_cball"/>
</th>
<th>product</th>
<th>price</th>
</tr>
</thead>
<tbody id="j_tb">
<tr>
<td>
<input type="checkbox"/>
</td>
<td>iphone</td>
<td>8000</td>
</tr>
<tr>
<td>
<input type="checkbox"/>
</td>
<td>huawei</td>
<td>9000</td>
</tr>
<tr>
<td>
<input type="checkbox"/>
</td>
<td>sony</td>
<td>3000</td>
</tr>
</tbody>
</table>
<style>
.bg{
background-color: blueviolet;
}
</style>
<script>
var j_cbAll = document.getElementById('j_cball');
var j_tbs = document.getElementById('j_tb').getElementsByTagName('input');
j_cbAll.onclick = function(){
for(var i = 0; i < j_tbs.length; i++){
j_tbs[i].checked = this.checked;
}
}
var flg = true;
for(var i = 0; i < j_tbs.length; i++){
j_tbs[i].onclick = function(){
for(var i = 0; i < j_tbs.length; i++){
if(j_tbs[i].checked){
flg = false;
break;
}
}
j_cbAll.checked = flg;
}
}
</script>
</body>
</html>