<body>
<div>
<input type="checkbox" name="" id="chose" value="" />
<input type="checkbox" name="" id="" value="" />
<input type="checkbox" name="" id="" value="" />
</div>
</body>
<script>
var all = document.getElementById("chose");
var allCheck = document.getElementsByTagName("input");
var content = 0;
all.onclick = function(){
for(var i=0;i<allCheck.length;i++){
allCheck[i].checked = (this.checked)?true:false;
content = (this.checked)?allCheck.length-1:0;
}
}
for(var i=1;i<allCheck.length;i++){
allCheck[i].onclick = function(){
if(!this.checked){
all.checked = false;
content--;
}else{
content++
}
totle(content);
}
}
function totle(content){
if(content==allCheck.length-1){
all.checked = true;
}
}
</script>