Add index param to select (#198)

* add index param to select

cdn/radash.esm.js

@@ -170,10 +170,13 @@ const objectify = (array, getKey, getValue = (item) => item) => {
   );
 };
 const select = (array, mapper, condition) => {
-  return array.reduce((acc, item) => {
-    if (!condition(item))
+  if (!array)
+    return [];
+  return array.reduce((acc, item, index) => {
+    if (!condition(item, index))
       return acc;
-    return [...acc, mapper(item)];
+    acc.push(mapper(item, index));
+    return acc;
   }, []);
 };
 const max = (array, getter) => {

cdn/radash.js

@@ -173,10 +173,13 @@ var radash = (function (exports) {
     );
   };
   const select = (array, mapper, condition) => {
-    return array.reduce((acc, item) => {
-      if (!condition(item))
+    if (!array)
+      return [];
+    return array.reduce((acc, item, index) => {
+      if (!condition(item, index))
         return acc;
-      return [...acc, mapper(item)];
+      acc.push(mapper(item, index));
+      return acc;
     }, []);
   };
   const max = (array, getter) => {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "radash",
-  "version": "10.2.0",
+  "version": "10.3.0",
   "description": "Functional utility library - modern, simple, typed, powerful",
   "main": "dist/cjs/index.cjs",
   "module": "dist/esm/index.mjs",

src/array.ts

@@ -217,16 +217,19 @@ export const objectify = <T, Key extends string | number | symbol, Value = T>(
  * Select performs a filter and a mapper inside of a reduce,
  * only iterating the list one time.
  *
- * Ex. select([1, 2, 3, 4], x => x*x, x > 2) == [9, 16]
+ * @example
+ * select([1, 2, 3, 4], x => x*x, x > 2) == [9, 16]
  */
 export const select = <T, K>(
   array: readonly T[],
-  mapper: (item: T) => K,
-  condition: (item: T) => boolean
+  mapper: (item: T, index: number) => K,
+  condition: (item: T, index: number) => boolean
 ) => {
-  return array.reduce((acc, item) => {
-    if (!condition(item)) return acc
-    return [...acc, mapper(item)]
+  if (!array) return []
+  return array.reduce((acc, item, index) => {
+    if (!condition(item, index)) return acc
+    acc.push(mapper(item, index))
+    return acc
   }, [] as K[])
 }
 

src/tests/array.test.ts

@@ -250,6 +250,24 @@ describe('array module', () => {
   })
 
   describe('select function', () => {
+    test('does not fail on bad input', () => {
+      assert.deepEqual(
+        _.select(
+          null as unknown as any[],
+          x => x,
+          x => x
+        ),
+        []
+      )
+      assert.deepEqual(
+        _.select(
+          undefined as unknown as any[],
+          x => x,
+          x => x
+        ),
+        []
+      )
+    })
     test('returns mapped and filtered values', () => {
       const list = [
         { group: 'a', word: 'hello' },
@@ -274,6 +292,15 @@ describe('array module', () => {
       )
       assert.deepEqual(result, [])
     })
+    test('works with index', () => {
+      const letters = ['a', 'b', 'c', 'd']
+      const result = _.select(
+        letters,
+        (l, idx) => `${l}${idx}`,
+        (l, idx) => idx > 1
+      )
+      assert.deepEqual(result, ['c2', 'd3'])
+    })
   })
 
   describe('max function', () => {