Custom JavaScript to remember input range state

custom-sliders.js

<script
  src="https://code.jquery.com/jquery-3.4.1.slim.min.js"
  integrity="sha256-pasqAKBDmFT4eHoN2ndd6lN370kFiGUFyTiUHWhU7k8="
  crossorigin="anonymous"></script>
<script type="text/javascript">

    var SELECTORS = {
        LABELS: '.modtype_label',
        RANGES: 'input[type="range"]'
    };

    var registerEventListeners = function(root) {
        var labelActivities = root.find(SELECTORS.LABELS);

        var rangeValues = getStorage();

        labelActivities.each(function(aindex, activity) {
            var ranges = $(activity).find(SELECTORS.RANGES);
            var activityId = $(activity).attr('id');
            ranges.each(function(rindex, range) {
                var value = $(range).val();
                var rangeIdentifyer = activityId + '-range-' + rindex;
                if (rangeValues.hasOwnProperty(rangeIdentifyer)) {
                    $(range).val(rangeValues[rangeIdentifyer]);
                }
                $(range).attr('data-value', value);
                $(range).attr('id', rangeIdentifyer);
            })
            $(activity).on('change', SELECTORS.RANGES, function() {
                var value = $(this).val();
                var rangeid = $(this).attr('id');
                setStorage(rangeid, value);
            })
        });
    };

    var setStorage = function(rangeid, value) {
        var inputranges = {};
        if (storedValue = localStorage.getItem('cie-input-ranges')) {
            if (IsJsonString(storedValue)) {
                var inputranges = JSON.parse(storedValue);
            }
        }
        inputranges[rangeid] = value;
        localStorage.setItem('cie-input-ranges', JSON.stringify(inputranges));
    }

    var getStorage = function() {
        var storedValue = {};
        var storedObject = localStorage.getItem('cie-input-ranges');
        if (IsJsonString(storedObject)) {
            storedValue = JSON.parse(storedObject);
        }
        return storedValue;
    }

    var IsJsonString = function(str) {
        if (str === null) {
            return false;
        }
        try {
            JSON.parse(str);
        } catch (e) {
            localStorage.removeItem('cie-input-ranges');
            return false;
        }
        return true;
    }

    var root = $('.course-content');
    registerEventListeners(root);
</script>