注意点：
checkbox.checked = true;
checkbox.checked = false;
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>列表全选、全不选、反选</title>
</head>
<body>
<h1>最爱的水果列表</h1>
<hr>
<input type="checkbox" id="apple"><label for="apple">苹果</label><br><br>
<input type="checkbox" id="str"><label for="str">草莓</label><br><br>
<input type="checkbox" id="ban"><label for="ban">香蕉</label><br><br>
<input type="checkbox" id="liu"><label for="liu">榴莲</label><br><br>
<input type="checkbox" id="san"><label for="san">山竹</label><br><br>
<input type="checkbox" id="che"><label for="che">车厘子</label><br><br>
<button id="all">全选</button>
<button id="allNo">全不选</button>
<button id="reverse">反选</button>
</body>
<script>
var checkboxs = document.querySelectorAll('input[type=checkbox]');
var all = document.getElementById('all');
var allNo = document.getElementById('allNo');
var reverse = document.getElementById('reverse');
all.onclick = function(){
for(var i in checkboxs){
checkboxs[i].checked = true;
}
}
allNo.onclick = function(){
for(var i in checkboxs){
checkboxs[i].checked = false;
}
}
reverse.onclick = function(){
for(var i in checkboxs){
checkboxs[i].checked = ! checkboxs[i].checked;
}
}
</script>
</html>