bezier curve function generator returns a function(t) that accepts [0..1] and returns an [x,y] pair at that point.

bezzy.js

function bezzy() {
    var pts = Array.prototype.slice.call(arguments),
        funcs = [];
    function b1(p1, p2) {
        return function(t) {
            var i = 1 - t;
            return [p1[0]*i+p2[0]*t, p1[1]*i+p2[1]*t];
        }
    }
    function b2(p1, p2, p3) {
        return function(t) {
            return b1(b1(p1, p2)(t), b1(p2, p3)(t))(t);
        }
    }
    function b3(p1, p2, p3, p4) {
        return function(t) {
            return b1(b2(p1, p2, p3)(t), b2(p2, p3, p4)(t))(t);
        }
    }
    switch (pts.length) {
        case 4:
            return b3.apply(null, pts);
        case 3:
            return b2.apply(null, pts);
        case 2:
            return b1.apply(null, pts);
        default:
            throw "unrecognized number of points!";
    }
}