Delete characters from my last focused text field when div in pressed

I have a div (button) that when is pressed it deletes the characters of an specific text field. Now I am trying to change the code in a way that delete the characters of the last focused text field.

This is the code that only delete the characters of one text field:

$(".delete").on("mousedown",function(evt) {
        var nameInput = document.querySelector("#name")
        var cursorPosition = nameInput.selectionStart;

    $("#firstName").val(
        function(index, value){
            return value.substr(0,cursorPosition - 1) + value.substr(cursorPosition);
    });

    nameInput.selectionStart = cursorPosition - 1;
    nameInput.selectionEnd = cursorPosition - 1;

    return false;
});

And this is what I haver for now:

$(".delete").on("mousedown",function(evt) {

    var lastFocused;
    $(".item").focusout( function(e) {
      lastFocused = e.target;
    });

    var cursorPosition = lastFocused.selectionStart;

    lastFocused.val(
        function(index, value){
            return value.substr(0,cursorPosition - 1) + value.substr(cursorPosition);
    });

    lastFocused.selectionStart = cursorPosition - 1;
    lastFocused.selectionEnd = cursorPosition - 1;

    return false;
});

The HTML:

<div class="delete key-btn">
<input id="firstName" name="firstName" type="text" class="item" required/>
<input id="firstName" name="firstName" type="text" class="item" required/>

In console, I'm getting the error: "Cannot read property 'selectionStart' of undefined". Can someone please tell me how to achive this? Thanks

This works:

// 1. this has to be declared globally
var lastFocused;

// 2. you need to set the event handler for the 'item' elements outside of the delete handler
//    I'd also suggest using the 'focus' event here instead of 'focusout'
$(".item").focus(function(e) {
    lastFocused = e.target;
});

$(".delete").on("mousedown", function(evt) {
    // 3. need the null check if none of the inputs have been focused yet
    if (!lastFocused) {
        return;
    }

    var cursorPosition = lastFocused.selectionStart;

    // 4. need to wrap this in the jQuery function to use val()
    $(lastFocused).val(
        function(index, value){
            return value.substr(0,cursorPosition - 1) + value.substr(cursorPosition);
    });

    lastFocused.selectionStart = cursorPosition - 1;
    lastFocused.selectionEnd = cursorPosition - 1;

    return false;
});