clear Rect doesnt work
<p>I'm kinda new to all this in trying to learn java script. I would like to add to a drawing program buttons with different functions. But I got problems with the first one, of course. I'm trying to have a button to clear the entire canvas. But somehow it doesn't work. Can you please help?</p>

<pre><code>&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
&lt;meta charset="utf-8"&gt;
&lt;script type="text/javascript" 
src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"&gt;&lt;/script&gt;
&lt;script type="text/javascript"&gt;
$(document).ready(function() {


var cb_canvas = null;
var cb_ctx = null;
var cb_lastPoints = null;
var cb_easing = 0.4;

// Setup event handlers
window.onload = init;
function init(e) {
cb_canvas = document.getElementById("cbook");

cb_lastPoints = Array();

if (cb_canvas.getContext) {
    cb_ctx = cb_canvas.getContext('2d');
    cb_ctx.lineWidth = 2;
    cb_ctx.strokeStyle = "rgb(0, 0, 0)";
    cb_ctx.beginPath();

    cb_canvas.onmousedown = startDraw;
    cb_canvas.onmouseup = stopDraw;
    cb_canvas.ontouchstart = startDraw;
    cb_canvas.ontouchstop = stopDraw;
    cb_canvas.ontouchmove = drawMouse;
}
}





function startDraw(e) {
if (e.touches) {
    // Touch event
    for (var i = 1; i &lt;= e.touches.length; i++) {
        cb_lastPoints[i] = getCoords(e.touches[i - 1]); // Get info for 
finger #1
    }
}
else {
    // Mouse event
    cb_lastPoints[0] = getCoords(e);
    cb_canvas.onmousemove = drawMouse;
}

return false;
}

// Called whenever cursor position changes after drawing has started
function stopDraw(e) {
e.preventDefault();
cb_canvas.onmousemove = null;
}

function drawMouse(e) {
if (e.touches) {
    // Touch Enabled
    for (var i = 1; i &lt;= e.touches.length; i++) {
        var p = getCoords(e.touches[i - 1]); // Get info for finger i
        cb_lastPoints[i] = drawLine(cb_lastPoints[i].x, cb_lastPoints[i].y, 
p.x, p.y);
    }
}
else {
    // Not touch enabled
    var p = getCoords(e);
    cb_lastPoints[0] = drawLine(cb_lastPoints[0].x, cb_lastPoints[0].y, p.x,     
p.y);
}
cb_ctx.stroke();
cb_ctx.closePath();
cb_ctx.beginPath();

return false;
}

// Draw a line on the canvas from (s)tart to (e)nd
function drawLine(sX, sY, eX, eY) {
cb_ctx.moveTo(sX, sY);
cb_ctx.lineTo(eX, eY);
    return { x: eX, y: eY };
}

// Get the coordinates for a mouse or touch event
function getCoords(e) {
if (e.offsetX) {
        return { x: e.offsetX, y: e.offsetY };
    }
    else if (e.layerX) {
        return { x: e.layerX, y: e.layerY };
    }
    else {
        return { x: e.pageX - cb_canvas.offsetLeft, y: e.pageY -     
cb_canvas.offsetTop };
}
}

$("clear").onclick=function(){clearAll()};

function clearAll() {
        var canvas = $("#cbook");
        var ctx = canvas.get(0).getContext("2d");
        ctx.clearRect(0, 0, canvas.width, canvas.height);   
}

});



&lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;canvas id="cbook" width="500" height="333"&gt;&lt;/canvas&gt;


&lt;button id="clear"&gt;Clean Up&lt;/button&gt;

&lt;/body&gt;
&lt;/html&gt;
</code></pre>
