Point in Polygon

pointInPolygon.js

function isPointInPath(x, y, poly){
        var num = poly.length,
        i = 0,
        j = num - 1,
        c = false;
        for( ; i < num; ++i ) {
                if ( ((poly[i][1] > y) != (poly[j][1] > y)) 
                    && (x < (poly[j][0] - poly[i][0]) * (y - poly[i][1]) / (poly[j][1] - poly[i][1]) + poly[i][0]))
                    c = !c;
                j = i;
        }
        return c;
}

b = [[0,0],[1,3],[2,0],[3,3]];

console.log(isPointInPath(3,6, a));