JavaScript function that animates an element's numeric style in a certain amount of time

element-animate.js

var animate = (function () {
    "use strict";

    var ret;

    ret =  function (elem, style, unit, from, to, time) {
        var start, timer;
        if (!elem) {
            return;
        }
        if (time == null) {
            time = 400;
        }
        start = new Date().getTime();
        timer = setInterval(function () {
            var step = Math.min(1, (new Date().getTime() - start) / time);
            elem.style[style] = (from + step * (to - from)) + unit;
            if (step === 1) {
                clearInterval(timer);
            }
        }, 25);
        elem.style[style] = from + unit;
    };

    return ret;
}());