var descriptions = {};

function onQuerySucceeded(sender, args) {

    var listItemInfo = '';
    var listItemEnumerator = collListItem.getEnumerator();
        
    while (listItemEnumerator.moveNext()) {
        var oListItem = listItemEnumerator.get_current();
		descriptions[oListItem.get_item('Title')] = oListItem.get_item('Description')
    }

	console.log(descriptions);
}

function onQueryFailed(sender, args) {

    alert('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace());
}

function retrieveListItemsInclude() {

    var clientContext = new SP.ClientContext.get_current();
    var oList = clientContext.get_web().get_lists().getByTitle('Hello');

    var camlQuery = new SP.CamlQuery();
    camlQuery.set_viewXml('<View><RowLimit>100</RowLimit></View>');
    this.collListItem = oList.getItems(camlQuery);

    clientContext.load(collListItem, 'Include(Title, Description)');

    clientContext.executeQueryAsync(Function.createDelegate(this, this.onQuerySucceeded), Function.createDelegate(this, this.onQueryFailed));
}

retrieveListItemsInclude();

const result = document.getElementById('notificationArea');
const selector = document.getElementById('CategoriesLookup_3f44dee7-b4ba-4e0f-9a4c-84f4420dfaf6_$LookupField')
selector.addEventListener('change', (event) => {
  let selectedOption = selector.options[selector.selectedIndex].innerHTML
  result.textContent = descriptions[selectedOption];
});