Canvas - requestAnimationFrame

HTML

<canvas id="canvas"></canvas>

CSS

#canvas {
    border: 1px solid silver;
    width: 100%;
}

JavaScript

var x = 0; 
function drawIt() { 
    window.requestAnimationFrame(drawIt); 
    var canvas = document.getElementById('canvas'); 
    var c = canvas.getContext('2d');
    c.fillStyle = "red"; 
    c.fillRect(x,50,1,1); 
    x+=1; 
} 

//window.requestAnimationFrame(drawIt);
drawIt();