performanceNow.js

/**
 * Copyright 2013-2014, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule performanceNow
 * @typechecks
 */

var performance = require('performance');

/**
 * Detect if we can use `window.performance.now()` and gracefully fallback to
 * `Date.now()` if it doesn't exist. We need to support Firefox < 15 for now
 * because of Facebook's testing infrastructure.
 */
if (!performance || !performance.now) {
  performance = Date;
}

var performanceNow = performance.now.bind(performance);

module.exports = performanceNow;