timer.es6

class Timer {
    constructor () {
        this.timers = {};
    }
    
    /**
     * Starts the timer for the provided identifier
     * @usage timer.start('myTimer');
     * @param {string} id The identifier to use for this particular timer.
     */
    start (id) {
        this.timers[id] = this.timers[id] || {};
        this.timers[id].start = performance.now();
    }
    
    /**
     * Ends the timer for the provided identifier
     * Calculates the delta between start and end times
     * @usage timer.end('myTimer');
     * @param {string} id The identifier for this particular timer.
     */
    end (id) {
        this.timers[id] = this.timers[id] || {};
        this.timers[id].end = performance.now();
        
        this.timers[id].delta = this.timers[id].hasOwnProperty('start')? this.timers[id].end - this.timers[id].start: 0;
    }
    
    /**
     * Gets a specific timer's information
     * @usage console.log(timer.get('myTimer');
     * @param {string} id The identifier of the timer being retrieved
     * @return {object} The timer object of the provided identifier
     */
    get (id) {
        return this.timers[id];
    }
    
    /**
     * Returns all timers
     * @usage console.table(timer.list());
     * @return {object} Returns the internal timers object
     */
    list () {
        return this.timers;
    }
}

timer.js

var Timer = function () {
    this.timers = {};
};

Timer.prototype.start = function (id) {
    this.timers[id] = this.timers[id] || {};
    this.timers[id].start = performance.now();
};

Timer.prototype.end = function (id) {
    this.timers[id] = this.timers[id] || {};
    this.timers[id].end = performance.now();
    
    this.timers[id].delta = this.timers[id].hasOwnProperty('start')? this.timers[id].end - this.timers[id].start: 0;
};

Timer.prototype.get = function (id) {
    return this.timers[id];
};

Timer.prototype.list = function () {
    return this.timers;
};