JS实现复选框全选反选

function checkAll()
{
var object = document.getElementsByName("changeAll");//全选按钮状态
var sonObject=document.getElementsByName("choose");
var length = sonObject.length;
if(object[0].checked){
for (var i = 0; i < length; i++)
{
sonObject[i].checked=true;
}
}
else{
for (var j = 0; j < length; j++)
{
sonObject[j].checked=false;
}
}
}