conversant/ad-libs.js

/**
 * @module perfMarker
 * @desc A module to mark the timestamps for script performance
 */

'use strict';

/**
 * Used to manage instances of perfMarker.
 * @private
 * @type {Object}
 */
var instanceRegistry = {};

/*
 *
 * @type {Function}
 */
var now = function () {
    return window.performance && performance.now ? performance.now() : +(new Date());
};

var startTime = (function () {
    if (window.performance && performance.timing) {
        return performance.timing.navigationStart;
    } else {
        return +(new Date());
    }
}());

/*
 *
 * @constructor
 */
var PerfMarker = function () {

    var self = this,
        timeMap = {},
        timeline = [];

    self.start = function (name) {
        if (timeMap[name]) {
            timeline[timeMap[name]].start = now();
        } else {
            timeMap[name] = timeline.length;
            timeline.push({
                name: name,
                start: now(),
                end: 0
            });
        }
        return this;
    };

    self.end = function (name) {
        if (typeof timeMap[name] !== 'undefined') {
            timeline[timeMap[name]].end = now();
        } else {
            throw new Error('No start time set for time marked as', name);
        }
        return this;
    };

    self.run = function (fn, iterate) {
        var i = 0;
        if (iterate) {
            for (i = 0; i < iterate; i++) {
                fn();
            }
        } else {
            fn();
        }
        return this;
    };

    self.getTimeline = function () {
        var timelineMap = [],
            time,
            calculatedStart;

        var makeEntry = function (time) {
            var entry;
            if (window.performance && performance.now){
                calculatedStart = time.start;
             } else {
                calculatedStart = time.start - startTime;
            }
            entry = {
                name: time.name,
                startTime: calculatedStart,
                duration: (time.end - time.start) >= 0 ? (time.end - time.start) : null,
                toString: function () {
                    return 'name: ' + this.name +
                        '\tstartTime:\t' + this.startTime +
                        '\tduration:\t' + this.duration;
                }
            };
            return entry;
        };

        for (time in timeline) {
            if (timeline.hasOwnProperty(time)) {
                timelineMap.push(makeEntry(timeline[time]));
            }
        }
        return timelineMap;
    };

    self.report = function () {
        return self.getTimeline().join('\n');
    };
};


var markerFactory = function () {
    return new PerfMarker();
};


var markerProvider = function (pkgName) {
    if (!instanceRegistry[pkgName]) {
        instanceRegistry[pkgName] = new PerfMarker();
    }
    return instanceRegistry[pkgName];
};


/**
 * @desc Creates a new instance of PerfMarker.
 * @static
 * @returns {PerfMarker}
 */
module.exports.factory = markerFactory;

/**
 * @desc Ties into an existing instance of PerfMarker.
 * @static
 * @param {String} [pkgName] The name of the instance.
 * @returns {PerfMarker}
 */
module.exports.provider = markerProvider;