通过JS模拟Win10桌面的拖拉框选，只实现了一个方向的框选，如何实现多方向的框选呢

var Mil = false;

var NewDiv = document.createElement('div');



function getMousePos(event) {

    var e = event || window.event;

    var scrollX = document.documentElement.scrollLeft || document.body.scrollLeft;

    var scrollY = document.documentElement.scrollTop || document.body.scrollTop;

    var x = e.pageX || e.clientX + scrollX;

    var y = e.pageY || e.clientY + scrollY;

    return { 'x': x, 'y': y };

}

function  Mi(e) {

    document.body.appendChild(NewDiv);

    NewDiv.id = 'Move_div';

    move_div = document.getElementById("Move_div");

    var m_down_x = getMousePos(e).x;

    var m_down_y= getMousePos(e).y;

    move_div.style.left = m_down_x + "px";

    move_div.style.top = m_down_y + "px";

    move_div.style.width = m_down_x - parseInt(move_div.style.left) +"px";

    move_div.style.height = m_down_y - parseInt(move_div.style.top) +"px";

    Mil = true;



}

function move(e){

    if(Mil){

        move_div = document.getElementById("Move_div");

        var m_move_x = getMousePos(e).x;

        var m_move_y= getMousePos(e).y;

        move_div.style.width = m_move_x - parseInt(move_div.style.left) +"px";

        move_div.style.height = m_move_y - parseInt(move_div.style.top) +"px";

    }

}

function up(){

    Mil = false;

    document.body.removeChild(document.getElementById("Move_div"));

}