Form valid combinations from CSV selection options

Question

I am building a form with multiple select option fields. I am trying to only show the next field if it exists as a combination in the CSV file I am reading in. It's working fine right now and I am using onchange for each select field to call the next function.

Is there a way to reduce to the code and make it more efficient?

var lines = [];
var datas = [];

$(document).ready(function() {
$.ajax({
    type: "GET",
    url: "data.txt",
    dataType: "text",
    success: function(data) {
        processData(data);
    }
});
});

function processData(allText) {
var allTextLines = allText.split(/\r\n|\n/);
var headers = allTextLines[0].split(',');

for (var i = 1; i < allTextLines.length; i++) {
    var data = allTextLines[i].split(',');
    if (data.length == headers.length) {

        var tarr = [];
        for (var j = 0; j < headers.length; j++) {
            tarr.push(data[j]);
        }
        lines.push(tarr);
    }
}
datas = lines;

regulatory = []
for (var i = 0; i < datas.length; i++) {
    if ($.inArray(datas[i][0], regulatory) == -1) {
        regulatory.push(datas[i][0]);
    }
}
for (var i = 0; i < regulatory.length; i++) {
    addOption(document.drop_list.Regulatory, regulatory[i], regulatory[i]);
}

 }

 function SelectDMZ() {
removeAllOptions(document.drop_list.DMZ);
addOption(document.drop_list.DMZ, "Select!", "Select!");
for (var i = 0; i < datas.length; i++) {
    if (document.drop_list.Regulatory.value == datas[i][0]) {
        if ($("#DMZ option:contains('" + datas[i][1] + "')").length == 0) {
            addOption(document.drop_list.DMZ, datas[i][1], datas[i][1]);
        }
    }
}
}

 function SelectCoS() {
removeAllOptions(document.drop_list.CoS);
addOption(document.drop_list.CoS, "Select!", "Select!");
for (var i = 0; i < datas.length; i++) {
    if (document.drop_list.Regulatory.value == datas[i][0] & document.drop_list.DMZ.value == datas[i][1]) {
        if ($("#CoS option:contains('" + datas[i][2] + "')").length == 0) {
            addOption(document.drop_list.CoS, datas[i][2], datas[i][2]);
        }
    }
}
}

 function SelectExclusive() {
removeAllOptions(document.drop_list.Exclusive);
addOption(document.drop_list.Exclusive, "Select!", "Select!");
for (var i = 0; i < datas.length; i++) {
    if (document.drop_list.Regulatory.value == datas[i][0] & document.drop_list.DMZ.value == datas[i][1] & document.drop_list.CoS.value == datas[i][2]) {
        if ($("#Exclusive option:contains('" + datas[i][3] + "')").length == 0) {
            addOption(document.drop_list.Exclusive, datas[i][3], datas[i][3]);
        }
    }
}
  }

  function SelectNetwork() {
removeAllOptions(document.drop_list.Network);
addOption(document.drop_list.Network, "Select!", "Select!");
for (var i = 0; i < datas.length; i++) {
    if (document.drop_list.Regulatory.value == datas[i][0] & document.drop_list.DMZ.value == datas[i][1] & document.drop_list.CoS.value == datas[i][2] & document.drop_list.Exclusive.value == datas[i][3]) {
        if ($("#Network option:contains('" + datas[i][4] + "')").length == 0) {
            addOption(document.drop_list.Network, datas[i][4], datas[i][4]);
        }
    }
}
  }

  function SelectCommunity() {
removeAllOptions(document.drop_list.Community);
addOption(document.drop_list.Community, "Select!", "Select!");
for (var i = 0; i < datas.length; i++) {
    if (document.drop_list.Regulatory.value == datas[i][0] & document.drop_list.DMZ.value == datas[i][1] & document.drop_list.CoS.value == datas[i][2] & document.drop_list.Exclusive.value == datas[i][3] & document.drop_list.Network.value == datas[i][4]) {
        if ($("#Community option:contains('" + datas[i][5] + "')").length == 0) {
            addOption(document.drop_list.Community, datas[i][5], datas[i][5]);
        }
    }
}
}



function check_select() {
 if (document.drop_list.Platform.value == "Select!"){
 alert("Please select a platform!");
 return false;
 }
 }

 function removeAllOptions(selectbox) {
var i;
for (i = selectbox.options.length - 1; i >= 0; i--) {
    //selectbox.options.remove(i);
    selectbox.remove(i);
}
  }

 function addOption(selectbox, value, text) {
var optn = document.createElement("OPTION");
optn.text = text;
optn.value = value;

selectbox.options.add(optn);
 }