Updating line between divs in javascript

I'm trying to make a web page, where people can click on two objects and it creates a line between those two. But I want to go further on and be able to connect the last one with another one. This is the code I have so far.

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
<style type="text/css">
    img {
        padding: 1px;
        margin: 2px;
        float: left;
        background-color: #99BC99
    }
    img.selected {
        padding: 2px;
        margin: 4px;        
        background-color: #E13300
    }
</style>
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script type="text/javascript">

$(document).ready(function() {
    $('img').click(function(){
        $(this).toggleClass('selected');
        });
    });

function connect(div1, div2, color, thickness) {
    var off1 = getOffset(div1);
    var off2 = getOffset(div2);
    // bottom right
    var x1 = off1.left + off1.width;
    var y1 = off1.top + off1.height;
    // top right
    var x2 = off2.left + off2.width;
    var y2 = off2.top;
    // distance
    var length = Math.sqrt(((x2-x1) * (x2-x1)) + ((y2-y1) * (y2-y1)));
    // center
    var cx = ((x1 + x2) / 2) - (length / 2);
    var cy = ((y1 + y2) / 2) - (thickness / 2);
    // angle
    var angle = Math.atan2((y1-y2),(x1-x2))*(180/Math.PI);
    // make hr
    var htmlLine = "<div style='padding:0px; margin:0px; height:" + thickness + "px; background-color:" + color + "; line-height:1px; position:absolute; left:" + cx + "px; top:" + cy + "px; width:" + length + "px; -moz-transform:rotate(" + angle + "deg); -webkit-transform:rotate(" + angle + "deg); -o-transform:rotate(" + angle + "deg); -ms-transform:rotate(" + angle + "deg); transform:rotate(" + angle + "deg);' />";
    //
    document.body.innerHTML += htmlLine; 
}

function getOffset( el ) {
    var _x = 0;
    var _y = 0;
    var _w = el.offsetWidth|0;
    var _h = el.offsetHeight|0;
    while( el && !isNaN( el.offsetLeft ) && !isNaN( el.offsetTop ) ) {
        _x += el.offsetLeft - el.scrollLeft;
        _y += el.offsetTop - el.scrollTop;
        el = el.offsetParent;
    }
    return { top: _y, left: _x, width: _w, height: _h };
}

window.testIt = function() {
    var div1 = document.getElementById('div1')
    var div2 = document.getElementById('div2')
    connect(div1, div2, "#0F0", 5);
}
</script>

</head>

<body>
<script type="text/javascript">

</script>
  <a onclick="testIt();">Draw line</a>
  <span style="position: absolute; left: 933px; top: 211px;"> <img src="Untitled-2.jpg" alt="" width="35" height="35" id="div1"/></span>
  <span style="position: absolute; left: 304px; top: 190px;"> <img src="Untitled-3.jpg" alt="" width="35" height="35" id="div2"/></span>
  <span style="position: absolute; left: 756px; top: 264px;"> <img src="Untitled-4.jpg" alt="" width="35" height="35" id="div3"/></span>
  <span style="position: absolute; left: 365px; top: 395px;"> <img src="Untitled-6.jpg" alt="" width="35" height="35" id="div4"/></span>
  <span style="position: absolute; left: 129px; top: 302px;"> <img src="Untitled-5.jpg" alt="" width="35" height="35" id="div5"/></span>
  <span style="position: absolute; left: 504px; top: 261px;"> <img src="Untitled-7.jpg" alt="" width="35" height="35" id="div6"/></span>
  <span style="position: absolute; left: 650px; top: 393px;"> <img src="Untitled-8.jpg" alt="" width="35" height="35" id="div7"/></span>
  <span style="position: absolute; left: 283px; top: 26px;"> <img src="Untitled-9.jpg" alt="" width="35" height="35" id="div8"/></span>
  <span style="position: absolute; left: 593px; top: 35px;"> <img src="Untitled-10.jpg" alt="" width="35" height="35" id="div9"/></span>
  <span style="position: absolute; left: 784px; top: 42px;"> <img src="Untitled-1.jpg" alt="" width="35" height="35" id="div10"/></span>
</body>
</html>

But it stops with the first 2 divs. How can I update the div. Say I want div1 to be the previous div2 and div2 to be where i click. Thanks in advance and I apologize for the stupidity of the question. Best Regards.

You will need to cache the last element clicked.

See this fiddle: http://jsfiddle.net/RY6dM/

Based on your code and not doing any major changes:

$('img').click(function(){
    var $elem1 = $(this).parent();  // cache the span
    var $elem2 = $('span.last');    // cache the span with class last
    $(this).toggleClass('selected');
    if ($elem2.length > 0) {        // for the first time there is no cached element
         connect($elem1[0], $elem2[0], "#0F0", 5);
    } else { 
        $elem1.addClass('last');     // for subsequent clicks, cache last element
    }
    $('span').removeClass('last');    // remove class last from all spans
    $elem1.addClass('last');          // add class last to current element
});

Also, instead of: