A benchmark utility that measures the execution times of functions in an object

Benchmarks.js

/*
Usage:
            this.benchmarks = new Benchmarks({
                target: this,
                functions: ['performLookups', 'createIsotope', 'updateIsotope', 'fitVideos', 'applyRandomSize']
            });
*/
/**
 * A benchmark utility that measures the execution times of functions in an object, if enabled.
 * Disabled by default.
 * Enabled/disabled state is persisted in browser storage, e.g. survives page refresh.
 *
 * @param {Object} options - A configuration object
 * @param {Object} options.target - The target object that contains the functions
 * @param {Array} options.functions - Names of the functions in the target that should be benchmarked
 * @param {Object} [storage=window.localStorage] - A persistence object that supports the web storage API
 * @param {Object} [logger=window.console] - An object with a `log` function. Defaults to window.console
 */
function Benchmarks(options) {
    options = options || {};
    var target = options.target;
    var functions = options.functions;
    var storage = options.storage || window.localStorage;
    var logger = options.logger || window.console;
    var backups = {};
    var lsKey = 'Benchmarks.enabled';

    if (storage.getItem != undefined && !!storage.getItem(lsKey)) {
        setup();
    }

    this.enable = function () {
        setup();
        storage.setItem(lsKey, true);
    };
    this.disable = function () {
        teardown();
        storage.removeItem(lsKey);
    };

    function setup() {
        functions.forEach(function (name) {
            var fn = backups[name] || target[name];
            backups[name] = fn;
            target[name] = function () {
                var started = performance.now();
                fn.apply(target, arguments);
                logger.log(fn.name + ' done in ' + (performance.now() - started) + 'ms');
            };
            Object.defineProperty(target[name], 'name', { value: 'Benchmarked' + fn.name });
        });
    }

    function teardown() {
        functions.forEach(function (name) {
            target[name] = backups[name];
        });
    }
}