/** * @fileoverview * A utility for accurately measuring time. * To use: * --- * var timer = new Timer(); * timer.start(); * ... pass some time ... * var timeDifference = timer.timeElapsed(); * --- * Or, you can use the `time` and `relativeTime` * to do some measurement yourself. */ /** * @constructor */ var Timer = function () {}; /** * Used to store the start time of a timer action. * Updated when calling `timer.start`. */ Timer.prototype.startTime = 0; /** * Return the currently known absolute time, in ms precision. * @returns {number} ms elapsed since 1 January 1970 00:00:00 UTC. */ Timer.prototype.time = Date.now ? function () { return Date.now(); } : function () { return new Date().getTime(); }; /** * Returns a time accurate relative to other times produced by this function. * If possible, will use sub-millisecond precision. * If not, will use millisecond precision. * Not guaranteed to produce the same absolute values per-system. * @returns {number} ms-scale accurate time relative to other relative times. */ Timer.prototype.relativeTime = (typeof self !== 'undefined' && self.performance && 'now' in self.performance) ? function () { return self.performance.now(); } : function () { return this.time(); }; /** * Start a timer for measuring elapsed time, * at the most accurate precision possible. */ Timer.prototype.start = function () { this.startTime = this.relativeTime(); }; /** * Check time elapsed since `timer.start` was called. * @returns {number} Time elapsed, in ms (possibly sub-ms precision). */ Timer.prototype.timeElapsed = function () { return this.relativeTime() - this.startTime; }; module.exports = Timer;