Incomplete mesh intersection

<script>
function Point(x,y)
{
    this.x=x;
    this.y=y;
}
var mouse={down:1,pos:new Point(-1,-1)};
var docVals = false;
function Distance(a,b)
{
    return Math.pow(a.x-b.x,2)+Math.pow(a.y-b.y, 2);
}
function project(pStart,angle,size)
{
    return{x:pStart.x+Math.cos(angle)*size,y:pStart.y+Math.sin(angle)*size};
}
function getAngle(line)
{
    var dx = line.end.x-line.start.x;
    var dy = line.end.y-line.start.y;
    return Math.atan2(dy,dx);
}
function Intersects(lineA,lineB)
{
    var denom = ((lineA.end.x - lineA.start.x) * (lineB.end.y - lineB.start.y)) - ((lineA.end.y - lineA.start.y) * (lineB.end.x - lineB.start.x));
    if (denom == 0) return false;
    var numer = ((lineA.start.y - lineB.start.y) * (lineB.end.x - lineB.start.x)) - ((lineA.start.x - lineB.start.x) * (lineB.end.y - lineB.start.y));
    var r = numer / denom;
    var numer2 = ((lineA.start.y - lineB.start.y) * (lineA.end.x - lineA.start.x)) - ((lineA.start.x - lineB.start.x) * (lineA.end.y - lineA.start.y));
    var s = numer2 / denom;
    if ((r < 0 || r > 1) || (s < 0 || s > 1)) return false;
    return {x:(lineA.start.x - -(r * (lineA.end.x - lineA.start.x))),y:lineA.start.y - - (r * (lineA.end.y - lineA.start.y)),numer:[numer/denom,numer2/denom]};
}
function drawCircle(G,x,y,rad)
{
    G.arc(x, y, rad, 0, Math.PI*2, true);
}
function drawLines()
{
    if(!docVals)docVals =
    [document.getElementById("lineasx"),document.getElementById("lineasy"),
    document.getElementById("lineaex"),document.getElementById("lineaey"),
    document.getElementById("linebsx"),document.getElementById("linebsy"),
    document.getElementById("linebex"),document.getElementById("linebey")];
    var lineA = {start:new Point(docVals[0].value,docVals[1].value),end:new Point(docVals[2].value,docVals[3].value),angle:false,dist:false};
    var lineB = {start:new Point(docVals[4].value,docVals[5].value),end:new Point(docVals[6].value,docVals[7].value),angle:false,dist:false};
    lineA.angle = getAngle(lineA);
    lineB.angle = getAngle(lineB);
    lineA.dist = Math.sqrt(Distance(lineA.start,lineA.end));
    lineB.dist = Math.sqrt(Distance(lineB.start,lineB.end));
    var i = Intersects(lineA,lineB);
    var angle = false;
    var canvas = document.getElementById("canvas");
    var Graphics = canvas.getContext("2d");
    Graphics.strokeStyle="#F00";
    Graphics.beginPath();
    Graphics.fillStyle="#FFF";
    Graphics.clearRect(0,0,600,400);
    Graphics.beginPath();
    Graphics.stroke();
    Graphics.beginPath();
    Graphics.moveTo(lineB.start.x,lineB.start.y);
    Graphics.lineTo(lineB.end.x,lineB.end.y);
    Graphics.stroke();
    Graphics.beginPath();
    Graphics.moveTo(lineA.start.x,lineA.start.y);
    Graphics.lineTo(lineA.end.x,lineA.end.y);
    Graphics.stroke();
    if(i)
    {
        Graphics.beginPath();
        drawCircle(Graphics,i.x,i.y,7);
        Graphics.stroke();
        Graphics.beginPath();
        Graphics.moveTo(i.x,i.y);
        Graphics.lineTo(lineA.end.x,lineA.end.y);
        Graphics.stroke();
    }
    var distances =
    [{dist:Distance(mouse.pos,lineA.start),pos:lineA.start,id:"lineas"},
    {dist:Distance(mouse.pos,lineA.end),pos:lineA.end,id:"lineae"},
    {dist:Distance(mouse.pos,lineB.start),pos:lineB.start,id:"linebs"},
    {dist:Distance(mouse.pos,lineB.end),pos:lineB.end,id:"linebe"}];
    distances.sort(function(a,b){return a.dist>b.dist});
    if(distances[0].dist<2500)
    {
        Graphics.beginPath();
        Graphics.moveTo(mouse.pos.x,mouse.pos.y);
        Graphics.lineTo(distances[0].pos.x,distances[0].pos.y);
        Graphics.stroke();
        if(mouse.down==0)
        {
            document.getElementById(distances[0].id+"x").value=mouse.pos.x;
            document.getElementById(distances[0].id+"y").value=mouse.pos.y;
        }
    }
    if(i)
    {
        var P = project(i,lineB.angle-(lineA.angle-lineB.angle)+Math.PI,(i.numer[0])*lineA.dist);
        Graphics.beginPath();
        Graphics.moveTo(i.x,i.y);
        Graphics.lineTo(P.x,P.y);
        Graphics.stroke();
    }
}
function mouseDown(b)
{
    mouse.down = b;
    drawLines();
}
function mouseMove(event)
{
    mouseDown(mouse.down*2);
    mouse.pos.x = event.offsetX;
    mouse.pos.y = event.offsetY;
    drawLines();
}
</script>
<body onmouseup="mouseDown(1)">
<canvas width="600" height="400" style="border:1px #000 solid"
id="canvas" onmousemove="mouseMove(event)"
onmousedown="mouseDown(0)"></canvas><br>
<input id="lineasx" type="number" value="10" oninput="drawLines()"></input>,
<input id="lineasy" type="number" value="10" oninput="drawLines()"></input> to
<input id="lineaex" type="number" value="390" oninput="drawLines()"></input>,
<input id="lineaey" type="number"value="390" oninput="drawLines()"></input>
<br>
<br>
<input id="linebsx" type="number" value="10" oninput="drawLines()"></input>,
<input id="linebsy" type="number" value="390" oninput="drawLines()"></input> to
<input id="linebex" type="number" value="390" oninput="drawLines()"></input>,
<input id="linebey" type="number" value="10" oninput="drawLines()"></input>
<br>
<br>
<div id="res"></div>
<script>
drawLines();
</script>
</body>

























function Distance(a,b)
{
    return Math.pow(a.x-b.x,2)+Math.pow(a.y-b.y, 2);
}
function project(pStart,angle,size)
{
    return{x:pStart.x+Math.cos(angle)*size,y:pStart.y+Math.sin(angle)*size};
}
function getAngle(line)
{
    var dx = line.end.x-line.start.x;
    var dy = line.end.y-line.start.y;
    return Math.atan2(dy,dx);
}
function Intersects(line,mesh)
{
    for(var i in mesh)
    {
        var denom = ((line.end.x - line.start.x) * (mesh[i].end.y - mesh[i].start.y)) - ((line.end.y - line.start.y) * (mesh[i].end.x - mesh[i].start.x));
        if (denom == 0) return false;
        var numer = ((line.start.y - mesh[i].start.y) * (mesh[i].end.x - mesh[i].start.x)) - ((line.start.x - mesh[i].start.x) * (mesh[i].end.y - mesh[i].start.y));
        var r = numer / denom;
        var numer2 = ((line.start.y - mesh[i].start.y) * (line.end.x - line.start.x)) - ((line.start.x - mesh[i].start.x) * (line.end.y - line.start.y));
        var s = numer2 / denom;
        if (!((r < 0 || r > 1) || (s < 0 || s > 1)))
        {
            var thisOne = {start:false,end:false};
            thisOne.start = project(i,mesh[i].angle-(line.angle-mesh[i].angle)+Math.PI,r*line.dist);
            thisOne.end = {x:(line.start.x - -(r * (line.end.x - line.start.x))),y:line.start.y - - (r * (line.end.y - line.start.y)),numer:[numer/denom,numer2/denom]};
        }
    }
    return {end:line.start,path:[]};
}

<script>
var abc = [1,2,3];

</script>