JavaScript全选与取消全选

function selectAll(){
var obj = document.fom.elements;
for (var i=0;i<obj.length;i++){
if (obj[i].name == "delid"){
obj[i].checked = true;
}
}
}

function unselectAll(){
var obj = document.fom.elements;
for (var i=0;i<obj.length;i++){
if (obj[i].name == "delid"){
if (obj[i].checked==true) obj[i].checked = false;
else obj[i].checked = true;
}
}
}