Pupulate Donor Perfect Checkboxes Based on Query String Parameter

<script>
// Get the parameter from the Query String
function getParameterByName(name, url) {
    if (!url) url = window.location.href;
    name = name.replace(/[\[\]]/g, "\\$&");
    var regex = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)"),
        results = regex.exec(url);
    if (!results) return null;
    if (!results[2]) return '';
    return decodeURIComponent(results[2].replace(/\+/g, " "));
}
function check(id) {
    document.getElementById(id).checked = true;
}
var amount = getParameterByName('donationAmount');

// Target the Donate Buttons
function getElementsByIDSubString(type, substring) {
	var allNodes = document.getElementsByTagName(type), item;
	var elements = [];
	for (var i = 0, len = allNodes.length; i < len; i++) {
		item = allNodes[i];
		if (item.id && item.id.indexOf(substring) !== -1) {
			elements.push(item);
		}
	}
	return elements;
}
var donationInputs = getElementsByIDSubString("input", "giftPledgeAmount_ucGPOtherAmountRbl");

// Get this list of Labels to add "active" class.
var amountLabels = document.querySelectorAll('[onclick="rblGPOtherAmountChangedMOF(this)"]');

// TODO Abstract this 
if(amount) {
	if (amount == 'five') {
		check(donationInputs[0].id);
		amountLabels[0].classList.add('active');
	} else if (amount == 'ten') {
		check(donationInputs[1].id);
		amountLabels[1].classList.add('active');
	} else if (amount == 'fifty') {
		check(donationInputs[2].id);
		amountLabels[2].classList.add('active');
	} else if (amount == 'one_hundred') {
		check(donationInputs[3].id);
		amountLabels[3].classList.add('active');
	} else { // It's Other Amount
		check(donationInputs[4].id);
		amountLabels[4].classList.add('active');
		// Target Other Text
		var otherTextArea = getElementsByIDSubString("input", "giftPledgeAmount_ucGPOtherAmountTxt_")[0];
		otherTextArea.style.backgroundColor = 'white';
		otherTextArea.style.color = 'black';
		otherTextArea.value = '0.00';
	}
}
</script>