Remove usage of Array#fill (#20071)

gaearon · gaearon · commit 8e5adfbd7e60 · 2020-10-22T12:59:20.000+01:00
diff --git a/packages/react-reconciler/src/ReactFiberLane.js b/packages/react-reconciler/src/ReactFiberLane.js
@@ -640,7 +640,13 @@ export function higherLanePriority(
 }
 
 export function createLaneMap<T>(initial: T): LaneMap<T> {
-  return new Array(TotalLanes).fill(initial);
+  // Intentionally pushing one by one.
+  // https://v8.dev/blog/elements-kinds#avoid-creating-holes
+  const laneMap = [];
+  for (let i = 0; i < TotalLanes; i++) {
+    laneMap.push(initial);
+  }
+  return laneMap;
 }
 
 export function markRootUpdated(

Original file line number	Diff line number	Diff line change
`@@ -640,7 +640,13 @@ export function higherLanePriority(`
`640`	`640`	`}`
`641`	`641`
`642`	`642`	`export function createLaneMap<T>(initial: T): LaneMap<T> {`
`643`		`- return new Array(TotalLanes).fill(initial);`
	`643`	`+ // Intentionally pushing one by one.`
	`644`	`+ // https://v8.dev/blog/elements-kinds#avoid-creating-holes`
	`645`	`+ const laneMap = [];`
	`646`	`+ for (let i = 0; i < TotalLanes; i++) {`
	`647`	`+ laneMap.push(initial);`
	`648`	`+ }`
	`649`	`+ return laneMap;`
`644`	`650`	`}`
`645`	`651`
`646`	`652`	`export function markRootUpdated(`