Qty Input Addition/Subtraction for IE10+ (w/ JQuery for delegation.. feel free to change to vanilla JS) https://codepen.io/AndresInSpace/pen/xMyeVO

qty-input-counter

var editQty = (function(){

    function editValue(e) {
        var input = e.target.nextElementSibling || e.target.previousElementSibling;
        input.value = counter(e.target.classList.contains('plus'),input.value);
    }

    function counter(add,x) {
        return add ? ++x : (x > 1 ? --x : x);
    }

    return function() {
        var group = jQuery('.qty-wrapper');
        group.on('click', '.qty-counter', editValue);
    }
}());
editQty();