//create and fill polygon
CanvasRenderingContext2D.prototype.fillPolygon = function (pointsArray, fillColor, strokeColor) {
if (pointsArray.length <= 0) return;
this.moveTo(pointsArray[0][0], pointsArray[0][1]);
for (var i = 0; i < pointsArray.length; i++) {
this.lineTo(pointsArray[i][0], pointsArray[i][1]);
}
if (strokeColor != null && strokeColor != undefined)
this.strokeStyle = strokeColor;
if (fillColor != null && fillColor != undefined) {
this.fillStyle = fillColor;
this.fill();
}
}
//And you can use this method as
var polygonPoints = [[10,100],[20,75],[50,100],[100,100],[10,100]];
context.fillPolygon(polygonPoints, '#F00','#000');