Create a star and give a background color using Javascript

I want to draw a star and give it a background color by using Javascript. This is the jsfiddle :-

http://jsfiddle.net/earnubs/TZasK/

But red background color is covering whole sqaure area, I just want to give background to that star only.

This is the Javascript :-

var canvas, ctx, length = 15; // length of the star's arm



// grab a reference to the 2d context from canvas element

canvas = document.getElementById("star");

ctx = canvas.getContext("2d");



// move into the middle of the canvas, just to make room

ctx.translate(30, 30);



// initial offset rotation so our star is straight

ctx.rotate((Math.PI * 1 / 10));



// make a point, 5 times

for (var i = 5; i--;) {

    // draw line up

    ctx.lineTo(0, length);

    // move origin to current same location as pen

    ctx.translate(0, length);

    // rotate the drawing board

    ctx.rotate((Math.PI * 2 / 10));

    // draw line down

    ctx.lineTo(0, -length);

    // again, move origin to pen...

    ctx.translate(0, -length);

    // ...and rotate, ready for next arm

    ctx.rotate(-(Math.PI * 6 / 10));

}

// last line to connect things up

ctx.lineTo(0, length);

ctx.closePath();

// stroke the path, you could also .fill()

ctx.stroke();