Simple color animation

gistfile1.js

    function animateColor(element, property, start_hex, end_hex, duration) {
        var start = parseHexColor(start_hex),
            end = parseHexColor(end_hex);
        var start_time = new Date().getTime();
        var timer = setInterval(function() {
            var elapsed_millis = new Date().getTime() - start_time;
            if (elapsed_millis >= duration) {
                clearInterval(timer);
                element.css(property, end_hex);
                return;
            }
            var t = elapsed_millis/duration;
            var c = interpolateColor(start, end, t);
            element.css(property, c);
        }, 10);
    }
    function parseHexColor(hex_color) {
        var a = hex_color.match(/^#(..)(..)(..)$/);
        if (a == null)
            throw "Failed to parse hex color: " + hex_color;
        return [parseInt(a[1], 16), parseInt(a[2], 16), parseInt(a[3], 16)];
    }
    function toHexColor(color) {
        var h = function(n) {
            var x = Math.round(n).toString(16);
            return (x.length == 1) ? "0" + x : x;
        };
        return "#" + h(color[0]) + h(color[1]) + h(color[2]);
    }
    function interpolateColor(start, end, t) {
        var i = function(a, b) {
            return (1-t)*a + t*b;
        };
        return toHexColor([
            i(start[0], end[0]),
            i(start[1], end[1]),
            i(start[2], end[2])
        ]);
    }