Need help to find out the checklist name

Question

I have a code here in javascript , it wrks to populate a checklist based on the dropdownlist selection.

 

The code is as below

 

  <script type="text/javascript">
function populate(slct1, slct2) {
var s1 = document.getElementById(slct1);
var s2 = document.getElementById(slct2);
s2.innerHTML = "";
if (s1.value == "LowerPrimary") {
var optionArray = ["Std-1", "Std-2","Std-3","Std-4","Std-5"];
} else if (s1.value == "HighSchool") {
var optionArray = ["Std-6","Std-7","Std-8"];
} else if (s1.value == "Secondary") {
var optionArray = ["Std-9","Std-10"];
}
else if (s1.value == "HigherSecondary") {
var optionArray = ["Std-11","Std-12"];
}

for (var option in optionArray) {
if (optionArray.hasOwnProperty(option)) {
var pair = optionArray[option];
var checkbox = document.createElement("input");
checkbox.type = "checkbox";
checkbox.name = pair;
checkbox.value = pair;
s2.appendChild(checkbox);

var label = document.createElement('label')
label.htmlFor = pair;
label.appendChild(document.createTextNode(pair));

s2.appendChild(label);
s2.appendChild(document.createElement("br"));
}
}
}
</script>

 

 

html part 

 first drop down list

 <select id="slct1" name="slct1" onchange="populate(this.id, 'slct2')">
<option value=""></option>
<option value="LowerPrimary">LowerPrimary</option>
<option value="HighSchool">HighSchool</option>
<option value="Secondary">Secondary</option>
<option value="HigherSecondary">HigherSecondary</option>

</select>

//the populated checklist is displayed inside this div

  Choose Subcategory:
<div id="slct2"></div>

 

I need to get  the name of the second check list so that i can store the selected multivalues from the populated checklist . into the databse