Add index parameter to filterMap callback signature

dist/index.cjs

@@ -124,10 +124,13 @@ var Maybe = class _Maybe {
     if (isNothing(this._value)) return new _Maybe(null);
     const arr = this._value;
     const result = [];
-    for (const el of arr) {
-      const maybeVal = fn(el);
+    for (let i = 0; i < arr.length; i++) {
+      const el = arr[i];
+      if (el === void 0) continue;
+      const maybeVal = fn(el, i);
       if (!(maybeVal instanceof _Maybe)) return _Maybe.fromNullable(null);
-      if (isJust(maybeVal.value())) result.push(maybeVal.value());
+      const val = maybeVal.value();
+      if (isJust(val)) result.push(val);
     }
     return new _Maybe(result);
   }
@@ -315,8 +318,8 @@ var AsyncMaybe = class _AsyncMaybe {
       if (raw == null) return raw;
       if (!Array.isArray(raw)) return null;
       const values = await Promise.all(
-        raw.map(async (el) => {
-          const out = await fn(el);
+        raw.map(async (el, i) => {
+          const out = await fn(el, i);
           if (out instanceof _AsyncMaybe) return await out.value();
           if (out instanceof Maybe) return out.value();
           return out;

dist/index.d.cts

@@ -114,7 +114,7 @@ declare class AsyncMaybe<T> {
      * @param fn - A function returning a Maybe/AsyncMaybe/value for each element.
      * @returns A new AsyncMaybe containing the filtered/mapped array, or Nothing.
      */
-    filterMap<U, V>(this: AsyncMaybe<U[]>, fn: (value: U) => Maybe<V> | AsyncMaybe<V> | V | Promise<Maybe<V> | AsyncMaybe<V> | V>): AsyncMaybe<V[]>;
+    filterMap<U, V>(this: AsyncMaybe<U[]>, fn: (value: U, index: number) => Maybe<V> | AsyncMaybe<V> | V | Promise<Maybe<V> | AsyncMaybe<V> | V>): AsyncMaybe<V[]>;
     first<Us extends ReadonlyArray<AsyncMaybe<unknown> | Maybe<unknown>>>(fn: (value: T) => Us): AsyncMaybe<ExtractMaybeArrayValue<Us>>;
     /**
      * withDefault - Provides a default value if Nothing.
@@ -265,7 +265,7 @@ declare class Maybe<T> {
      * @param fn - A function mapping each element to a Maybe.
      * @returns A Maybe of the filtered/mapped array, or Nothing if empty.
      */
-    filterMap<U, V>(this: Maybe<U[]>, fn: (value: U) => Maybe<V>): Maybe<V[]>;
+    filterMap<U, V>(this: Maybe<U[]>, fn: (value: U, index: number) => Maybe<V>): Maybe<V[]>;
     /**
      * Returns the first Maybe to produce a non-Nothing value
      *
@@ -316,10 +316,10 @@ declare function filter<A>(predicate: (value: A) => boolean): {
     (m: Maybe<A>): Maybe<A>;
     (m: AsyncMaybe<A>): AsyncMaybe<A>;
 };
-declare function filterMap<A, B>(fn: (value: A) => Maybe<B>): {
+declare function filterMap<A, B>(fn: (value: A, index: number) => Maybe<B>): {
     <M extends Maybe<A[]> | AsyncMaybe<A[]>>(m: M): M extends AsyncMaybe<A[]> ? AsyncMaybe<B[]> : Maybe<B[]>;
 };
-declare function filterMap<A, B>(fn: (value: A) => AsyncMaybe<B>): {
+declare function filterMap<A, B>(fn: (value: A, index: number) => AsyncMaybe<B>): {
     (m: Maybe<A[]>): AsyncMaybe<B[]>;
     (m: AsyncMaybe<A[]>): AsyncMaybe<B[]>;
 };

dist/index.d.ts

@@ -114,7 +114,7 @@ declare class AsyncMaybe<T> {
      * @param fn - A function returning a Maybe/AsyncMaybe/value for each element.
      * @returns A new AsyncMaybe containing the filtered/mapped array, or Nothing.
      */
-    filterMap<U, V>(this: AsyncMaybe<U[]>, fn: (value: U) => Maybe<V> | AsyncMaybe<V> | V | Promise<Maybe<V> | AsyncMaybe<V> | V>): AsyncMaybe<V[]>;
+    filterMap<U, V>(this: AsyncMaybe<U[]>, fn: (value: U, index: number) => Maybe<V> | AsyncMaybe<V> | V | Promise<Maybe<V> | AsyncMaybe<V> | V>): AsyncMaybe<V[]>;
     first<Us extends ReadonlyArray<AsyncMaybe<unknown> | Maybe<unknown>>>(fn: (value: T) => Us): AsyncMaybe<ExtractMaybeArrayValue<Us>>;
     /**
      * withDefault - Provides a default value if Nothing.
@@ -265,7 +265,7 @@ declare class Maybe<T> {
      * @param fn - A function mapping each element to a Maybe.
      * @returns A Maybe of the filtered/mapped array, or Nothing if empty.
      */
-    filterMap<U, V>(this: Maybe<U[]>, fn: (value: U) => Maybe<V>): Maybe<V[]>;
+    filterMap<U, V>(this: Maybe<U[]>, fn: (value: U, index: number) => Maybe<V>): Maybe<V[]>;
     /**
      * Returns the first Maybe to produce a non-Nothing value
      *
@@ -316,10 +316,10 @@ declare function filter<A>(predicate: (value: A) => boolean): {
     (m: Maybe<A>): Maybe<A>;
     (m: AsyncMaybe<A>): AsyncMaybe<A>;
 };
-declare function filterMap<A, B>(fn: (value: A) => Maybe<B>): {
+declare function filterMap<A, B>(fn: (value: A, index: number) => Maybe<B>): {
     <M extends Maybe<A[]> | AsyncMaybe<A[]>>(m: M): M extends AsyncMaybe<A[]> ? AsyncMaybe<B[]> : Maybe<B[]>;
 };
-declare function filterMap<A, B>(fn: (value: A) => AsyncMaybe<B>): {
+declare function filterMap<A, B>(fn: (value: A, index: number) => AsyncMaybe<B>): {
     (m: Maybe<A[]>): AsyncMaybe<B[]>;
     (m: AsyncMaybe<A[]>): AsyncMaybe<B[]>;
 };