RN: Clean JSTimersExecution JS

Reviewed By: sahrens

Differential Revision: D3539098

fbshipit-source-id: f17a35c5d6a45627bd6961b6b06266fe254d3976

Libraries/JavaScriptAppEngine/System/JSTimers/JSTimersExecution.js

@@ -10,11 +10,12 @@
  */
 'use strict';
 
-var invariant = require('fbjs/lib/invariant');
-var keyMirror = require('fbjs/lib/keyMirror');
-var performanceNow = require('fbjs/lib/performanceNow');
-var warning = require('fbjs/lib/warning');
-var Systrace = require('Systrace');
+const Systrace = require('Systrace');
+
+const invariant = require('fbjs/lib/invariant');
+const keyMirror = require('fbjs/lib/keyMirror');
+const performanceNow = require('fbjs/lib/performanceNow');
+const warning = require('fbjs/lib/warning');
 
 let hasEmittedTimeDriftWarning = false;
 
@@ -23,7 +24,7 @@ let hasEmittedTimeDriftWarning = false;
  * external clock signal, all that's stored here is timerID, timer type, and
  * callback.
  */
-var JSTimersExecution = {
+const JSTimersExecution = {
   GUID: 1,
   Type: keyMirror({
     setTimeout: null,
@@ -43,9 +44,13 @@ var JSTimersExecution = {
    * if it was a one time timer (setTimeout), and not unregister it if it was
    * recurring (setInterval).
    */
-  callTimer: function(timerID) {
-    warning(timerID <= JSTimersExecution.GUID, 'Tried to call timer with ID ' + timerID + ' but no such timer exists');
-    var timerIndex = JSTimersExecution.timerIDs.indexOf(timerID);
+  callTimer(timerID) {
+    warning(
+      timerID <= JSTimersExecution.GUID,
+      'Tried to call timer with ID %s but no such timer exists.',
+      timerID
+    );
+    const timerIndex = JSTimersExecution.timerIDs.indexOf(timerID);
     // timerIndex of -1 means that no timer with that ID exists. There are
     // two situations when this happens, when a garbage timer ID was given
     // and when a previously existing timer was deleted before this callback
@@ -54,8 +59,8 @@ var JSTimersExecution = {
     if (timerIndex === -1) {
       return;
     }
-    var type = JSTimersExecution.types[timerIndex];
-    var callback = JSTimersExecution.callbacks[timerIndex];
+    const type = JSTimersExecution.types[timerIndex];
+    const callback = JSTimersExecution.callbacks[timerIndex];
 
     // Clear the metadata
     if (type === JSTimersExecution.Type.setTimeout ||
@@ -70,7 +75,7 @@ var JSTimersExecution = {
           type === JSTimersExecution.Type.setImmediate) {
         callback();
       } else if (type === JSTimersExecution.Type.requestAnimationFrame) {
-        var currentTime = performanceNow();
+        const currentTime = performanceNow();
         callback(currentTime);
       } else {
         console.error('Tried to call a callback with invalid type: ' + type);
@@ -87,19 +92,22 @@ var JSTimersExecution = {
    * This is called from the native side. We are passed an array of timerIDs,
    * and
    */
-  callTimers: function(timerIDs) {
-    invariant(timerIDs.length !== 0, 'Probably shouldn\'t call "callTimers" with no timerIDs');
+  callTimers(timerIDs) {
+    invariant(
+      timerIDs.length !== 0,
+      'Cannot call `callTimers` with an empty list of IDs.'
+    );
 
     JSTimersExecution.errors = null;
     timerIDs.forEach(JSTimersExecution.callTimer);
 
-    var errors = JSTimersExecution.errors;
+    const errors = JSTimersExecution.errors;
     if (errors) {
-      var errorCount = errors.length;
+      const errorCount = errors.length;
       if (errorCount > 1) {
         // Throw all the other errors in a setTimeout, which will throw each
         // error one at a time
-        for (var ii = 1; ii < errorCount; ii++) {
+        for (let ii = 1; ii < errorCount; ii++) {
           require('JSTimers').setTimeout(
             ((error) => { throw error; }).bind(null, errors[ii]),
             0
@@ -114,18 +122,18 @@ var JSTimersExecution = {
    * Performs a single pass over the enqueued immediates. Returns whether
    * more immediates are queued up (can be used as a condition a while loop).
    */
-  callImmediatesPass: function() {
+  callImmediatesPass() {
     Systrace.beginEvent('JSTimersExecution.callImmediatesPass()');
 
     // The main reason to extract a single pass is so that we can track
     // in the system trace
     if (JSTimersExecution.immediates.length > 0) {
-      var passImmediates = JSTimersExecution.immediates.slice();
+      const passImmediates = JSTimersExecution.immediates.slice();
       JSTimersExecution.immediates = [];
 
       // Use for loop rather than forEach as per @vjeux's advice
       // https://github.com/facebook/react-native/commit/c8fd9f7588ad02d2293cac7224715f4af7b0f352#commitcomment-14570051
-      for (var i = 0; i < passImmediates.length; ++i) {
+      for (let i = 0; i < passImmediates.length; ++i) {
         JSTimersExecution.callTimer(passImmediates[i]);
       }
     }
@@ -139,7 +147,7 @@ var JSTimersExecution = {
    * This is called after we execute any command we receive from native but
    * before we hand control back to native.
    */
-  callImmediates: function() {
+  callImmediates() {
     JSTimersExecution.errors = null;
     while (JSTimersExecution.callImmediatesPass()) {}
     if (JSTimersExecution.errors) {
@@ -152,7 +160,7 @@ var JSTimersExecution = {
   /**
    * Called from native (in development) when environment times are out-of-sync.
    */
-  emitTimeDriftWarning: function(warningMessage) {
+  emitTimeDriftWarning(warningMessage) {
     if (hasEmittedTimeDriftWarning) {
       return;
     }
@@ -160,7 +168,7 @@ var JSTimersExecution = {
     console.warn(warningMessage);
   },
 
-  _clearIndex: function(i) {
+  _clearIndex(i) {
     JSTimersExecution.timerIDs[i] = null;
     JSTimersExecution.callbacks[i] = null;
     JSTimersExecution.types[i] = null;