feat: add findLast/findLastIndex polyfill for Uint8Array (#363)

Author: dsherret

lib/pkg/dnt_wasm_bg.wasm

@@ -33,27 +33,84 @@ declare global {
       thisArg?: any,
     ): number;
   }
+  interface Uint8Array {
+    /**
+     * Returns the value of the last element in the array where predicate is true, and undefined
+     * otherwise.
+     * @param predicate findLast calls predicate once for each element of the array, in descending
+     * order, until it finds one where predicate returns true. If such an element is found, findLast
+     * immediately returns that element value. Otherwise, findLast returns undefined.
+     * @param thisArg If provided, it will be used as the this value for each invocation of
+     * predicate. If it is not provided, undefined is used instead.
+     */
+    findLast<S extends number>(
+      predicate: (
+          value: number,
+          index: number,
+          array: Uint8Array,
+      ) => value is S,
+      thisArg?: any,
+    ): S | undefined;
+    findLast(
+        predicate: (value: number, index: number, array: Uint8Array) => unknown,
+        thisArg?: any,
+    ): number | undefined;
+
+    /**
+     * Returns the index of the last element in the array where predicate is true, and -1
+     * otherwise.
+     * @param predicate findLastIndex calls predicate once for each element of the array, in descending
+     * order, until it finds one where predicate returns true. If such an element is found,
+     * findLastIndex immediately returns that element index. Otherwise, findLastIndex returns -1.
+     * @param thisArg If provided, it will be used as the this value for each invocation of
+     * predicate. If it is not provided, undefined is used instead.
+     */
+    findLastIndex(
+        predicate: (value: number, index: number, array: Uint8Array) => unknown,
+        thisArg?: any,
+    ): number;
+  }
+}
+
+function findLastIndex(self: any, callbackfn: any, that: any) {
+  const boundFunc = that === undefined ? callbackfn : callbackfn.bind(that);
+  let index = self.length - 1;
+  while (index >= 0) {
+    const result = boundFunc(self[index], index, self);
+    if (result) {
+      return index;
+    }
+    index--;
+  }
+  return -1;
+}
+
+function findLast(self: any, callbackfn: any, that: any) {
+  const index = self.findLastIndex(callbackfn, that);
+  return index === -1 ? undefined : self[index];
 }
 
 if (!Array.prototype.findLastIndex) {
   Array.prototype.findLastIndex = function (callbackfn: any, that: any) {
-    const boundFunc = that === undefined ? callbackfn : callbackfn.bind(that);
-    let index = this.length - 1;
-    while (index >= 0) {
-      const result = boundFunc(this[index], index, this);
-      if (result) {
-        return index;
-      }
-      index--;
-    }
-    return -1;
+    return findLastIndex(this, callbackfn, that);
   };
 }
 
 if (!Array.prototype.findLast) {
   Array.prototype.findLast = function (callbackfn: any, that: any) {
-    const index = this.findLastIndex(callbackfn, that);
-    return index === -1 ? undefined : this[index];
+    return findLast(this, callbackfn, that);
+  };
+}
+
+if (!Uint8Array.prototype.findLastIndex) {
+  Uint8Array.prototype.findLastIndex = function (callbackfn: any, that: any) {
+    return findLastIndex(this, callbackfn, that);
+  };
+}
+
+if (!Uint8Array.prototype.findLast) {
+  Uint8Array.prototype.findLast = function (callbackfn: any, that: any) {
+    return findLast(this, callbackfn, that);
   };
 }
 

rs-lib/src/polyfills/scripts/esnext.array-findLast.ts

@@ -42,3 +42,10 @@ Deno.test("should find last in array", () => {
     undefined,
   );
 });
+
+Deno.test("should find last for Uint8Array", () => {
+  assertEquals(new Uint8Array([1, 2, 3]).findLast(() => true), 3);
+  assertEquals(new Uint8Array([1, 2, 3]).findLastIndex(() => true), 2);
+  assertEquals(new Uint8Array([1, 2, 3]).findLast((v) => v == 2), 2);
+  assertEquals(new Uint8Array([1, 2, 3]).findLastIndex((v) => v == 2), 1);
+});