fix(isFinite): implement type predicate to narrow type to number

docs/ja/reference/compat/predicate/isFinite.md

@@ -50,4 +50,5 @@ isFinite(undefined); // false
 
 #### 戻り値
 
-(`boolean`): 値が有限な数値の場合は`true`、そうでない場合は`false`を返します。
+(`value is number`): 値が有限な数値の場合は`true`、そうでない場合は`false`を返します。  
+`true`を返す場合、TypeScriptは`value`の型を`number`に絞り込みます。

docs/ko/reference/compat/predicate/isFinite.md

@@ -50,4 +50,5 @@ isFinite(undefined); // false
 
 #### 반환 값
 
-(`boolean`): 값이 유한한 숫자이면 `true`, 아니면 `false`를 반환해요.
+(`value is number`): 값이 유한한 숫자이면 `true`, 아니면 `false`를 반환해요.  
+`true`를 반환하면 TypeScript가 `value`의 타입을 `number`로 좁혀줘요.

docs/reference/compat/predicate/isFinite.md

@@ -50,4 +50,5 @@ isFinite(undefined); // false
 
 #### Returns
 
-(`boolean`): Returns `true` if the value is a finite number, otherwise `false`.
+(`value is number`): Returns `true` if the value is a finite number, otherwise `false`.  
+When `true`, TypeScript narrows the type of `value` to `number`.

docs/zh_hans/reference/compat/predicate/isFinite.md

@@ -50,4 +50,5 @@ isFinite(undefined); // false
 
 #### 返回值
 
-(`boolean`): 如果值是有限数字则返回 `true`，否则返回 `false`。
+(`value is number`): 如果值是有限数字则返回 `true`，否则返回 `false`。  
+当返回 `true` 时，TypeScript 会将 `value` 的类型缩小为 `number`。

src/compat/predicate/isFinite.spec.ts

@@ -32,7 +32,17 @@ describe('isFinite', () => {
     expect(isFinite('-1')).toBe(false);
   });
 
-  it('should match the type of lodash', () => {
-    expectTypeOf(isFinite).toEqualTypeOf<typeof isFiniteLodash>();
+  it('should be compatible with lodash type', () => {
+    const lodashFn: typeof isFiniteLodash = isFinite;
+    expect(lodashFn(3)).toBe(true);
+    expect(lodashFn('3')).toBe(false);
+  });
+
+  it('should work as a type predicate', () => {
+    const value: unknown = 3;
+    if (isFinite(value)) {
+      expectTypeOf(value).toEqualTypeOf<number>();
+      expect(typeof value).toBe('number');
+    }
   });
 });

src/compat/predicate/isFinite.ts

@@ -1,8 +1,11 @@
 /**
  * Checks if `value` is a finite number.
  *
- * @param {any} value The value to check.
- * @returns {boolean} Returns `true` if `value` is a finite number, `false` otherwise.
+ * Acts as a type guard for `number` values — returning `true` only when `value`
+ * is of type `number` and finite (not `Infinity`, `-Infinity`, or `NaN`).
+ *
+ * @param {unknown} value The value to check.
+ * @returns {value is number} Returns `true` if `value` is a finite number, `false` otherwise.
  *
  * @example
  * ```typescript
@@ -13,8 +16,12 @@
  * console.log(isFinite(value1)); // true
  * console.log(isFinite(value2)); // false
  * console.log(isFinite(value3)); // false
+ *
+ * if (isFinite(value1)) {
+ *   console.log(value1.toFixed(2));
+ * }
  * ```
  */
-export function isFinite(value?: any): boolean {
+export function isFinite(value: unknown): value is number {
   return Number.isFinite(value);
 }