timers: use const as appropriate

PR-URL: #18486
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

Author: apapirovski

lib/timers.js

@@ -224,8 +224,8 @@ function TimersList(msecs, unrefed) {
 // adds listOnTimeout to the C++ object prototype, as
 // V8 would not inline it otherwise.
 TimerWrap.prototype[kOnTimeout] = function listOnTimeout(now) {
-  var list = this._list;
-  var msecs = list.msecs;
+  const list = this._list;
+  const msecs = list.msecs;
 
   debug('timeout callback %d', msecs);
   debug('now: %d', now);
@@ -322,7 +322,7 @@ function tryOnTimeout(timer, list) {
 function reuse(item) {
   L.remove(item);
 
-  var list = refedLists[item._idleTimeout];
+  const list = refedLists[item._idleTimeout];
   // if empty - reuse the watcher
   if (list !== undefined && L.isEmpty(list)) {
     debug('reuse hit');
@@ -346,7 +346,7 @@ function unenroll(item) {
     item._destroyed = true;
   }
 
-  var handle = reuse(item);
+  const handle = reuse(item);
   if (handle !== null) {
     debug('unenroll: list empty');
     handle.close();
@@ -429,7 +429,7 @@ exports.setTimeout = setTimeout;
 
 
 function ontimeout(timer, start) {
-  var args = timer._timerArgs;
+  const args = timer._timerArgs;
   if (typeof timer._onTimeout !== 'function')
     return promiseResolve(timer._onTimeout, args[0]);
   if (start === undefined && timer._repeat)
@@ -540,7 +540,7 @@ Timeout.prototype.unref = function() {
   if (this._handle) {
     this._handle.unref();
   } else if (typeof this._onTimeout === 'function') {
-    var now = TimerWrap.now();
+    const now = TimerWrap.now();
     if (!this._idleStart) this._idleStart = now;
     var delay = this._idleStart + this._idleTimeout - now;
     if (delay < 0) delay = 0;
@@ -551,7 +551,7 @@ Timeout.prototype.unref = function() {
       return;
     }
 
-    var handle = reuse(this);
+    const handle = reuse(this);
     if (handle !== null) {
       handle._list = undefined;
     }