<html>
<body onload="fillCanvas('white'); fillCanvas('purple');">
<script>
function fillCanvas(gradColor) {
    var c = document.getElementById(gradColor + 'Canvas');
    var ctx = c.getContext("2d");
    // Create solid-color gradient, with all stops same color
    var grd = ctx.createRadialGradient(75,50,5,90,60,100);
    grd.addColorStop(0,gradColor);
    grd.addColorStop(1,gradColor);
    // Fill with gradient, but effectively a solid fill
    ctx.fillStyle = grd;
    ctx.fillRect(0,0,200,100);
}
</script>
<canvas id="whiteCanvas" width="200" height="100"></canvas>
<br>
<canvas id="purpleCanvas" width="200" height="100"></canvas>
</body>
</html>