correct off by 1 error in findLast polyfills

github · Aug 14, 2023 · 7ed757a · 7ed757a
1 parent 2bfa6e2
commit 7ed757a
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Showing 4 changed files with 4 additions and 2 deletions.
diff --git a/src/array-findlast.ts b/src/array-findlast.ts
@@ -3,7 +3,7 @@ export function arrayFindLast<T>(
   pred: (this: T[], value: T, i: number, array: T[]) => boolean,
   recv = this
 ): T | void {
-  for (let i = this.length; i > 0; i -= 1) {
+  for (let i = this.length - 1; i >= 0; i -= 1) {
     if (pred.call(recv, this[i], i, this)) return this[i]
   }
 }

diff --git a/src/array-findlastindex.ts b/src/array-findlastindex.ts
@@ -3,7 +3,7 @@ export function arrayFindLastIndex<T>(
   pred: (this: T[], value: T, i: number, array: T[]) => boolean,
   recv = this
 ): number {
-  for (let i = this.length; i > 0; i -= 1) {
+  for (let i = this.length - 1; i >= 0; i -= 1) {
     if (pred.call(recv, this[i], i, this)) return i
   }
   return -1

diff --git a/test/array-findlast.js b/test/array-findlast.js
@@ -11,6 +11,7 @@ describe('arrayFindLast', () => {
 
   it('returns value that passes truthy', () => {
     expect(arrayFindLast.call([1, 2, 3], v => v === 3)).to.equal(3)
+    expect(arrayFindLast.call([1, 2, 3], v => v === 1)).to.equal(1)
     const arr = [1, 2, 3]
     const recv = {}
     expect(

diff --git a/test/array-findlastindex.js b/test/array-findlastindex.js
@@ -11,6 +11,7 @@ describe('arrayFindLastIndex', () => {
 
   it('returns value that passes truthy', () => {
     expect(arrayFindLastIndex.call([1, 2, 3], v => v === 3)).to.equal(2)
+    expect(arrayFindLastIndex.call([1, 2, 3], v => v === 1)).to.equal(0)
     const arr = [1, 2, 3]
     const recv = {}
     expect(