//全选、全不选的方法，formId是表单对应的id，selectName是需要全选全不选的name，buttonId是‘全选’('取消')按钮对应的id
function selectAll(formId,selectName,buttonId)
{
if(document.getElementById(buttonId).value=="全选"){ 
  var x = document.getElementsByName(selectName);     
  var c = x.length;
  for (i=0; i<c; i++){
   x[i].checked = true;
  }
  document.getElementById(buttonId).value="取消"
}else if (document.getElementById(buttonId).value=="取消"){
  document.getElementById(buttonId).value="全选"
  document.getElementById(formId).reset();
}
}