events: optimize arrayClone by copying forward

bmeurer · fhinkel · commit f2f997ad1e41 · 2017-01-04T14:56:41.000+01:00
Optimize arrayClone by copying forward. It's slightly faster (and more readable) to copy array elements in forward direction. This way it also avoids the ToBoolean and the postfix count operation. PR-URL: #10571 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
diff --git a/lib/events.js b/lib/events.js
@@ -477,9 +477,9 @@ function spliceOne(list, index) {
   list.pop();
 }
 
-function arrayClone(arr, i) {
-  var copy = new Array(i);
-  while (i--)
+function arrayClone(arr, n) {
+  var copy = new Array(n);
+  for (var i = 0; i < n; ++i)
     copy[i] = arr[i];
   return copy;
 }

Original file line number	Diff line number	Diff line change
`@@ -477,9 +477,9 @@ function spliceOne(list, index) {`
`477`	`477`	`list.pop();`
`478`	`478`	`}`
`479`	`479`
`480`		`-function arrayClone(arr, i) {`
`481`		`- var copy = new Array(i);`
`482`		`- while (i--)`
	`480`	`+function arrayClone(arr, n) {`
	`481`	`+ var copy = new Array(n);`
	`482`	`+ for (var i = 0; i < n; ++i)`
`483`	`483`	`copy[i] = arr[i];`
`484`	`484`	`return copy;`
`485`	`485`	`}`