Stopwatch inspired by https://tracy.nette.org/en/#toc-timing and iPhone's stopwatch for measuring duration in JS

Timer.js

var Stopwatch;
(function (console) {

    function createWatches() {
        var watches = {};

        function start(label) {

            label = label || "";
            watches[label] = new Date().getTime();
        }

        function lap(label) {
            label = label || "";
            if (typeof watches[label] === "undefined") {
                start(label);
            }
            return new Date().getTime() - watches[label];
        }

        function log(label) {
            console.log(lap(label));
        }

        return {
            start: start,
            lap: lap,
            log: log
        };
    }

    Stopwatch = createWatches();

})(console);