[ruslan_mart]

function onWheel(e) {
    var delta = e.deltaY || e.detail || e.wheelDelta;
    if(delta > 0 ? this.scrollTop < this.scrollHeight - this.clientHeight : this.scrollTop > 0) {
        this.scrollTop += 100 * (delta > 0 || -1);
        e.preventDefault();
    }
}

modal.addEventListener('wheel', onWheel);
modal.addEventListener('mousewheel', onWheel);