react-native/Libraries/Utilities/RCTRenderingPerf.js

/**
 * Copyright (c) 2015-present, 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 RCTRenderingPerf
 * @flow
 */
'use strict';

var ReactDefaultPerf = require('ReactDefaultPerf');

var invariant = require('invariant');

type perfModule = {
  start: () => void;
  stop: () => void;
}

var perfModules = [];
var enabled = false;

var RCTRenderingPerf = {
  // Once perf is enabled, it stays enabled
  toggle: function() {
    console.log('Render perfomance measurements enabled');
    enabled = true;
  },

  start: function() {
    if (!enabled) {
      return;
    }

    ReactDefaultPerf.start();
    perfModules.forEach((module) => module.start());
  },

  stop: function() {
    if (!enabled) {
      return;
    }

    ReactDefaultPerf.stop();
    ReactDefaultPerf.printInclusive();
    ReactDefaultPerf.printWasted();

    var totalRender = 0;
    var totalTime = 0;
    var measurements = ReactDefaultPerf.getLastMeasurements();
    for (var ii = 0; ii < measurements.length; ii++) {
      var render = measurements[ii].render;
      for (var nodeName in render) {
        totalRender += render[nodeName];
      }
      totalTime += measurements[ii].totalTime;
    }
    console.log('Total time spent in render(): ' + totalRender + 'ms');

    perfModules.forEach((module) => module.stop());
  },

  register: function(module: perfModule) {
    invariant(
      typeof module.start === 'function',
      'Perf module should have start() function'
    );
    invariant(
      typeof module.stop === 'function',
      'Perf module should have stop() function'
    );
    perfModules.push(module);
  }
};

module.exports = RCTRenderingPerf;