Code to generate a path object for https://github.com/JoelBesada/scrollpath from an array, using coords in px relational to current xy

Path Gen

//Code to generate a path object from an array, using coords in px relational to current xy

function do_with_args(func, args1, args2){
    args = jQuery.merge(args1, args2);
    console.log(func, args)
    return func.apply(null, args);
}


var OPERATIONS = {

    lineTo:
        function (path, xy, dx, dy){
            var x=xy[0], y=xy[1];
            var newx = x+dx;
                newy = y+dy;
            path.lineTo(newx, newy);
            return [newx, newy];
        },

    arc:
        function (path, xy, radius, rstart, rend, dir){
            var x=xy[0], y=xy[1],
                radians = rend - rstart;
            var chord_len = radius * Math.sin(radians/2),
                chord_angle = ((rstart - rend)/2) + (Math.PI/2);
            var dx = chord_len * Math.sin(chord_angle),
                dy = chord_len * Math.cos(chord_angle);
            var newx = x+dx,
                newy = y+dy;
            path.arc(newx, newy, radius, rstart, rend, dir)
            return [newx, newy];
        }

};


var START = [0, 0];

operations = [
        {method:'lineTo', args:[400, 0]},
        {method:'arc', args:[400, -Math.PI/2, Math.PI/2, false]}
    ];

CURRENT_POSITION = START;

var PATH = $.fn.scrollPath("getPath");

jQuery.each(operations, function(i, el){
    var method = el.method;
    var args = el.args;
    func = OPERATIONS[method];
    console.log([PATH, CURRENT_POSITION], args);
    CURRENT_POSITION = do_with_args(func, [PATH, CURRENT_POSITION], args);
})


// todo: use a vector class like this
function Vec2(x, y){
    // v = new Vec2(100, 200)
    this.x = x;
    this.y = y;
}
function V(x, y){
    // v = V(100, 200)
    // no "new" required
    return new Vec2(x, y);
}