I have set up previous focus storage in my document. When the button is clicked, a function gets executed. The value 0 is transported as a variable from the button to the function. In the function the new value is set to the previous focussed element. But it doesn't work. Why not? The reason why I do it this way is because I have more buttons, that give different values but only have to use the same function: setNewValue

Main script:

window.prevFocus = $();
// Catch any bubbling focusin events (focus does not bubble)
$(document).on('focusin', ':input', function () {
   // Test: Show the previous value
   $("#debug").html(prevFocus.attr("id"));
   // Save the previously clicked value for later
   window.prevFocus = $(this);
});

Button script

$("#butSetVal0").on({ 
    click: function(){
        newVal = 0;
        setNewValue(newVal);
    }
});

set new value script:

function setNewValue(newVal){
    prevFocus.val(newVal).trigger("input");
}