Tune Up jsFidler

assert.js

(function () {

    var output;

    function getOutput () {
        if (!output) {
            output = document.body.appendChild(document.createElement("pre"));
        }
        return output;
    }
    
    // Call these functions only after DOM Ready!
    
    window.log = function (text) {
        getOutput().innerHTML += text + "<br>";
    }

    window.assert = function (value, description) {
        var item = document.createElement("div");
        item.style.color = value ? "green" : "red";
        item.innerHTML = description;
        getOutput().appendChild(item);
    }

})();