<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<script>
window.onclick = function() {
var oAll = document.getElementById('all');
var oBox = document.getElementById('obox');
var oCh = document.getElementsByTagName('input')
oAll.onclick = function() {
for (var i = 0; i < oCh.length; i++) {
oCh[i].checked = true;
}
};
for (var i = 0; i < oCh.length; i++) {
oCh[i].onclick = function() {
var count = 0;
for (var i = 0; i < oCh.length; i++) {
if (oCh[i].checked) {
count++
console.log(count)
}
}
if (count == oCh.length - 1) {
oAll.checked = true;
} else {
oAll.checked = false;
}
}
}
}
</script>
<body>
<input type="checkbox" name="" id="all">全選
<hr>
<div id="box">
<input type="checkbox" name="" id="">
<input type="checkbox" name="" id="">
<input type="checkbox" name="" id="">
</div>
<script>
</script>
</body>
</html>
運行結果