JS触发器keydown事件

我有点困惑为什么这个代码不起作用：

$(document).keydown(function(e){
        if (e.keyCode == 39) {
            //RIGHT
            document.getElementById('col_detector_right').innerHTML="";
            col_jack('right');
            if(document.getElementById('col_detector_right').innerHTML!=""){
            }
            else{
                var left = document.getElementById('jack').style.left;
                var current_left = parseFloat(left);
                var new_left = current_left + 400;
                document.getElementById('jack').style.left = new_left+'px';
            }
            right = true;
            return false;
        }
        if (e.keyCode == 37) {
            //LEFT
            document.getElementById('col_detector_right').innerHTML="";
            col_jack('right');
            if(document.getElementById('col_detector_right').innerHTML!=""){
            }
            else{
                var left = document.getElementById('jack').style.left;
                var current_left = parseFloat(left);
                var new_left = current_left - 4;
                document.getElementById('jack').style.left = new_left+'px';
            }
            right = false;
            return false;
        }
        if (e.keyCode == 38) {
            //UP
            return false;
        }
        if (e.keyCode == 40) {
            //DOWN
            return false;
        }
        if (e.keyCode == 32) {
            //SPACE
            if(right==true){
                var top = document.getElementById('jack').style.top;
                var current_top = parseFloat(top);
                var new_top = current_top -40;
                document.getElementById('jack').style.top = new_top+'px';
                var left = document.getElementById('jack').style.left;
                var current_left = parseFloat(left);
                var new_left = current_left + 20;
                document.getElementById('jack').style.left = new_left+'px';
                right=false;
                var press = $.Event('keydown');
                press.which = 39;
                $(document).trigger(press);
            }
            else{
                var top = document.getElementById('jack').style.top;
                var current_top = parseFloat(top);
                var new_top = current_top -40;
                document.getElementById('jack').style.top = new_top+'px';
            }
            return false;
        }
    });

特别是这个位，不起作用：

var press = $.Event('keydown');
press.which = 39;
$(document).trigger(press);

为什么？这个想法是它应该触发右箭头键，但不是吗？什么都没有发生，要么没有触发它，要么没有正确检查keydown事件？我不知道是哪一个，还是别的什么？