How to get last Sharepoint list item by using lookup function

That formula will return the first item in your list where the "Title" column matches the Title control.

Are you saying that your lookup should return multiple results and that you want to return the last result? Or are you trying to simply lookup the last created item in that list?

Try the below code.

NWF$(document).ready(function()
{
NWF$('.title input').blur(function() //call function on change of title value
{
retrieveItemIdMax();
});
});
function retrieveItemIdMax()
{
var title = NWF$('.title input').val();
var clientContext = new SP.ClientContext.get_current();
var oList = clientContext.get_web().get_lists().getByTitle('Test Request Number');
var camlQuery = new SP.CamlQuery();
camlQuery.set_viewXml("<View><Query><OrderBy><FieldRef Name='ID' Ascending='False'/></OrderBy><Where><Eq><FieldRef Name='Currency'/><Value Type='Text'>"+title+"</Value></Eq></Where></Query><RowLimit>1</RowLimit></View>"); //ordering by Id and limiting query result to one row.
window.collListItem = oList.getItems(camlQuery);
clientContext.load(collListItem);
clientContext.executeQueryAsync(Function.createDelegate(this, this.onQuerySucceededNumber), Function.createDelegate(this, this.onQueryFailedNumber));
}
function onQuerySucceededNumber(sender, args)
{
if(collListItem)
{
var listItemEnumerator = collListItem.getEnumerator();
while (listItemEnumerator.moveNext())
{
var oListItem = listItemEnumerator.get_current();
var number = oListItem.get_item('ID'); //get item id value
NWF$('.cal').text(number); //set value to calculated field
}
}
}
function onQueryFailedNumber(sender, args) {
alert('Request failed. ' + args.get_message() + ' ' + args.get_stackTrace());
}