feat(compat): Add lastIndexOf function to es-toolkit/compat

benchmarks/bundle-size/lastIndexOf.spec.ts

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+import { describe, expect, it } from 'vitest';
+import { getBundleSize } from './utils/getBundleSize';
+
+describe('lastIndexOf bundle size', () => {
+  it('lodash-es', async () => {
+    const bundleSize = await getBundleSize('lodash-es', 'lastIndexOf');
+    expect(bundleSize).toMatchInlineSnapshot(`1586`);
+  });
+
+  it('es-toolkit', async () => {
+    const bundleSize = await getBundleSize('es-toolkit', 'lastIndexOf');
+    expect(bundleSize).toMatchInlineSnapshot(`235`);
+  });
+
+  it('es-toolkit/compat', async () => {
+    const bundleSize = await getBundleSize('es-toolkit/compat', 'lastIndexOf');
+    expect(bundleSize).toMatchInlineSnapshot(`435`);
+  });
+});

benchmarks/performance/lastIndexOf.bench.ts

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+import { bench, describe } from 'vitest';
+import { lastIndexOf as lastIndexOfToolkitCompat_ } from 'es-toolkit/compat';
+import { lastIndexOf as lastIndexOfLodash_ } from 'lodash';
+
+const indexOfToolkitCompat = lastIndexOfToolkitCompat_;
+const indexOfLodash = lastIndexOfLodash_;
+
+describe('lastIndexOf', () => {
+  const largeArray = Array(1_000_000)
+    .fill(0)
+    .map((_, i) => i);
+  const array = [1, 2, 3, 4, NaN, '1', '2', '3', '4', 'NaN', ...largeArray];
+
+  bench('es-toolkit/compat/lastIndexOf', () => {
+    indexOfToolkitCompat(array, 1);
+    indexOfToolkitCompat(array, NaN);
+    indexOfToolkitCompat(array, '1');
+    indexOfToolkitCompat(array, 'NaN', -5);
+    indexOfToolkitCompat(array, 'NaN', -100);
+  });
+
+  bench('lodash/lastIndexOf', () => {
+    indexOfLodash(array, 1);
+    indexOfLodash(array, NaN);
+    indexOfLodash(array, '1');
+    indexOfLodash(array, 'NaN', -5);
+    indexOfLodash(array, 'NaN', -100);
+  });
+});

docs/ja/reference/array/lastIndexOf.md

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+# lastIndexOf
+
+::: info
+この関数は互換性のために `es-toolkit/compat` でのみ利用可能です。代替となるネイティブ JavaScript API が存在するか、まだ完全に最適化されていない関数です。
+
+`es-toolkit/compat` からインポートした場合、[こちら](../../../compatibility.md)で説明されているように、lodash と全く同じように動作し、同じ機能を提供します。
+:::
+
+配列内の値の最後の出現位置のインデックスを検索します。
+
+このメソッドは `Array.prototype.lastIndexOf` と似ていますが、`NaN` 値も検索できます。
+`NaN` 以外の要素の比較には厳密等価演算子（`===`）を使用します。
+
+## シグネチャ
+
+```typescript
+function lastIndexOf<T>(array: T[], searchElement: T, fromIndex?: number): number;
+```
+
+### パラメータ
+
+- `array` (`T[]`): 検索対象の配列。
+
+::: info `array` は `ArrayLike<T>` または `null` または `undefined` も可能です
+
+lodash との完全な互換性を確保するため、`lastIndexOf` 関数は `array` を以下のように処理します：
+
+- `array` が `ArrayLike<T>` の場合、`Array.from(...)` を使用して配列に変換します。
+- `array` が `null` または `undefined` の場合、空の配列として扱われます。
+
+:::
+
+- `searchElement` (`T`): 検索する値。
+- `fromIndex` (`number`, オプション): 検索を開始するインデックス。
+
+### 戻り値
+
+(`number`): 配列内で値が最後に出現する位置のインデックス（0から始まる）。値が見つからない場合は `-1` を返します。
+
+## 使用例
+
+```typescript
+const array = [1, 2, 3, NaN, 1];
+lastIndexOf(array, 1); // => 4
+lastIndexOf(array, NaN); // => 3
+```

docs/ko/reference/compat/array/lastIndexOf.md

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+# lastIndexOf
+
+::: info
+이 함수는 호환성을 위한 `es-toolkit/compat` 에서만 가져올 수 있어요. 대체할 수 있는 네이티브 JavaScript API가 있거나, 아직 충분히 최적화되지 않았기 때문이에요.
+
+`es-toolkit/compat`에서 이 함수를 가져오면, [lodash와 완전히 똑같이 동작](../../../compatibility.md)해요.
+:::
+
+배열을 주어진 요소가 마지막으로 일치하는 인덱스를 찾아요.
+
+`Array.prototype.lastIndexOf`와 거의 같게 동작하는데요, `NaN` 값을 찾을 수 있어요.
+`NaN`이 아닌 요소를 비교할 때는 엄격 동등 연산(`===`)을 사용해요.
+
+## 인터페이스
+
+```typescript
+function lastIndexOf<T>(array: T[], searchElement: T, fromIndex?: number): number;
+```
+
+### 파라미터
+
+- `array` (`T[]`): 검색할 배열.
+
+::: info `array`는 `ArrayLike<T>`이거나 `null` 또는 `undefined`일 수 있어요
+
+lodash와 완전히 호환되도록 `lastIndexOf` 함수는 `array`를 다음과 같이 처리해요.
+
+- `array`가 `ArrayLike<T>`인 경우, 배열로 변환하기 위해 `Array.from(...)`을 사용해요.
+- `array`가 `null` 또는 `undefined`인 경우, 빈 배열로 간주돼요.
+
+:::
+
+- `searchElement` (`T`): 찾을 값.
+- `fromIndex` (`number`, 선택): 검색을 시작할 인덱스.
+
+### 반환 값
+
+(`number`): 배열에서 주어진 값과 마지막으로 일치하는 요소의 인덱스. 일치하는 요소를 찾을 수 없으면 `-1`을 반환해요.
+
+## 예시
+
+```typescript
+const array = [1, 2, 3, NaN, 1];
+lastIndexOf(array, 3); // => 4
+lastIndexOf(array, NaN); // => 3
+```

docs/reference/compat/array/lastIndexOf.md

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+# lastIndexOf
+
+::: info
+This function is only available in `es-toolkit/compat` for compatibility reasons. It either has alternative native JavaScript APIs or isn't fully optimized yet.
+
+When imported from `es-toolkit/compat`, it behaves exactly like lodash and provides the same functionalities, as detailed [here](../../../compatibility.md).
+:::
+
+Finds the index of the last occurrence of a value in an array.
+
+This method is similar to `Array.prototype.lastIndexOf`, but it also finds `NaN` values.
+It uses strict equality (`===`) to compare elements other than `NaN`.
+
+## Signature
+
+```typescript
+function lastIndexOf<T>(array: T[], searchElement: T, fromIndex?: number): number;
+```
+
+### Parameters
+
+- `array` (`T[]`): The array to search.
+
+::: info `array` can be `ArrayLike<T>` or `null` or `undefined`
+
+To ensure full compatibility with lodash, the `lastIndexOf` function processes `array` as follows:
+
+- If `array` is `ArrayLike<T>`, it converts it to an array using `Array.from(...)`.
+- If `array` is `null` or `undefined`, it is treated as an empty array.
+
+:::
+
+- `searchElement` (`T`): The value to search for.
+- `fromIndex` (`number`, optional): The index to start the search at.
+
+### Returns
+
+(`number`): The index (zero-based) of the last occurrence of the value in the array, or `-1` if the value is not found.
+
+## Example
+
+```typescript
+const array = [1, 2, 3, NaN, 1];
+lastIndexOf(array, 1); // => 4
+lastIndexOf(array, NaN); // => 3
+```

docs/zh_hans/reference/compat/array/lastIndexOf.md

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+# lastIndexOf
+
+::: info
+出于兼容性原因，此函数仅在 `es-toolkit/compat` 中提供。它可能具有替代的原生 JavaScript API，或者尚未完全优化。
+
+从 `es-toolkit/compat` 导入时，它的行为与 lodash 完全一致，并提供相同的功能，详情请见 [这里](../../../compatibility.md)。
+:::
+
+查找数组中最后一个出现的值的索引。
+
+此方法类似于 `Array.prototype.lastIndexOf`，但也能找到 `NaN` 值。
+它使用严格相等 (===) 来比较 `NaN` 以外的元素。
+
+## 签名
+
+```typescript
+function lastIndexOf<T>(array: T[], searchElement: T, fromIndex?: number): number;
+```
+
+### 参数
+
+- `array` (`T[]`): 要搜索的数组。
+
+::: info `array` 可以是 `ArrayLike<T>` 或 `null` 或 `undefined` 。
+
+为了确保与 lodash 的完全兼容性，`lastIndexOf` 函数会按照以下方式处理 `array`：
+
+- 如果 `array` 是 `ArrayLike<T>`，它会使用 `Array.from(...)` 将其转换为数组。
+- 如果 `array` 是 `null` 或 `undefined`，它会被视为一个空数组。
+
+:::
+
+- `searchElement` (`T`): 要搜索的值。
+- `fromIndex` (`number`, 可选): 开始搜索的索引。
+
+### 返回
+
+(`number`): 数组中最后一个出现的值的索引（以零为基准），如果未找到该值，则返回 `-1`。
+
+## 示例
+
+```typescript
+const array = [1, 2, 3, NaN, 1];
+lastIndexOf(array, 1); // => 4
+lastIndexOf(array, NaN); // => 3
+```

src/compat/array/lastIndexOf.spec.ts

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+import { describe, expect, it } from 'vitest';
+import { lastIndexOf } from './lastIndexOf';
+
+/**
+ * @see https://github.com/lodash/lodash/blob/v5-wip/test/findLastIndex-and-lastIndexOf.spec.js
+ */
+
+describe('lastIndexOf', () => {
+  const array = [1, 2, 3, 1, 2, 3];
+
+  it(`should return the index of the last matched value`, () => {
+    expect(lastIndexOf(array, 3)).toBe(5);
+  });
+
+  it(`should work with \`NaN\``, () => {
+    expect(lastIndexOf([1, 2, 3, NaN, 1, 2], NaN)).toBe(3);
+  });
+
+  it(`should work with a positive \`fromIndex\``, () => {
+    expect(lastIndexOf(array, 1, 2)).toBe(0);
+  });
+
+  it(`should work with a \`fromIndex\` >= \`length\``, () => {
+    const values = [6, 8, 2 ** 32, Infinity];
+    const expected = values.map(() => [-1, 3]);
+
+    const actual = values.map(fromIndex => [
+      lastIndexOf(array, undefined, fromIndex),
+      lastIndexOf(array, 1, fromIndex),
+    ]);
+
+    expect(actual).toEqual(expected);
+  });
+
+  it(`should work with a negative \`fromIndex\``, () => {
+    expect(lastIndexOf(array, 2, -3)).toBe(1);
+  });
+
+  it(`should work with a negative \`fromIndex\` <= \`-length\``, () => {
+    const values = [-6, -8, -Infinity];
+    const expected = values.map(() => 0);
+
+    const actual = values.map(fromIndex => lastIndexOf(array, 1, fromIndex));
+
+    expect(actual).toEqual(expected);
+  });
+
+  it(`should coerce \`fromIndex\` to an integer`, () => {
+    expect(lastIndexOf(array, 2, 4.2)).toBe(4);
+  });
+
+  it(`should return -1 for empty array or nullish values`, () => {
+    expect(lastIndexOf([], 1)).toBe(-1);
+    expect(lastIndexOf(null, 1)).toBe(-1);
+    expect(lastIndexOf(undefined, 1)).toBe(-1);
+  });
+});

src/compat/array/lastIndexOf.ts

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+import { isArrayLike } from '../predicate/isArrayLike';
+
+/**
+ * Finds the index of the last occurrence of a value in an array.
+ *
+ * This method is similar to `Array.prototype.lastIndexOf`, but it also finds `NaN` values.
+ * It uses strict equality (`===`) to compare elements.
+ *
+ * @template T - The type of elements in the array.
+ * @param {ArrayLike<T> | null | undefined} array - The array to search.
+ * @param {T} searchElement - The value to search for.
+ * @param {number} [fromIndex] - The index to start the search at.
+ * @returns {number} The index (zero-based) of the last occurrence of the value in the array, or `-1` if the value is not found.
+ *
+ * @example
+ * const array = [1, 2, 3, NaN, 1];
+ * lastIndexOf(array, 3); // => 4
+ * lastIndexOf(array, NaN); // => 3
+ */
+export function lastIndexOf<T>(array: ArrayLike<T> | null | undefined, searchElement: T, fromIndex?: number): number {
+  if (!isArrayLike(array) || array.length === 0) {
+    return -1;
+  }
+
+  const length = array.length;
+
+  let index = fromIndex ?? length - 1;
+  if (fromIndex != null) {
+    index = index < 0 ? Math.max(length + index, 0) : Math.min(index, length - 1);
+  }
+
+  // `Array.prototype.lastIndexOf` doesn't find `NaN` values, so we need to handle that case separately.
+  if (Number.isNaN(searchElement)) {
+    for (let i = index; i >= 0; i--) {
+      if (Number.isNaN(array[i])) {
+        return i;
+      }
+    }
+  }
+
+  return Array.from(array).lastIndexOf(searchElement, index);
+}