feat: Update "reduce" to allow uncurried call

src/reduce/reduce.js

@@ -1,25 +1,54 @@
+import { pipe } from "../pipe/pipe"
+
+const _reduce = (fn, defaultAcc, _source) => {
+  let acc = defaultAcc
+  const source = Array.isArray(_source) ? _source : [_source]
+
+  for (let i = 0, length = source.length; i < length; i++) {
+    acc = Array.isArray(fn)
+      ? pipe(...fn)(acc, source[i], i, source)
+      : fn(acc, source[i], i, source)
+  }
+
+  return acc
+}
+
 /**
  * Apply a function against an accumulator and each  element in the array (from
  * left to right) to reduce it to a single value.
  *
- * @param  {Function}  fn          Reduce function
- * @param  {Object}    defaultAcc  The default acc
- * @param  {Array}     source      Source input
+ * @param {Function} fn         Reduce function
+ * @param {Object}   defaultAcc Default accumulator value
+ * @param {Array}    source     Source input
  *
  * @return {mixed}
  *
  * @tag Array
  * @signature (fn: Function, defaultAcc: mixed) => (source: Array): mixed
+ * @signature (fn: Function, defaultAcc: mixed, source: Array): mixed
+ *
+ * @example
+ * const sum = (acc, item) => acc + item
+ *
+ * reduce(sum, 0, [1, 2])
+ * // => 3
  */
-const reduce = (fn, defaultAcc) => source => {
-  let acc = defaultAcc
-  const sourceArray = Array.isArray(source) ? source : [source]
-
-  for (let i = 0, length = sourceArray.length; i < length; i++) {
-    acc = fn(acc, sourceArray[i], i, sourceArray)
+export const reduce = (...params) => {
+  /*
+   * @signature (fn: Fn|Fn[], defaultAcc: mixed) => (source: []): mixed
+   *
+   * reduce(sum, 0)([1, 2])
+   * // => 3
+   */
+  if (params.length < 3) {
+    return source => _reduce(params[0], params[1], source)
   }
 
-  return acc
+  /*
+   * @signature (fn: Fn|Fn[], defaultAcc: mixed, source: []): mixed
+   *
+   * reduce(sum, 0, [1, 2])
+   * // => 3
+   */
+  return _reduce(...params)
 }
-
-export { reduce }

src/reduce/reduce.test.js

@@ -2,7 +2,17 @@ import test from "tape"
 import { reduce } from ".."
 
 test("reduce", t => {
-  t.equals(reduce((acc, next) => acc + next, 0)([1, 2, 3]), 6, "Sum an array")
+  t.equals(
+    reduce((acc, item) => acc + item, 0, [1, 2, 3]),
+    6,
+    "Sum an array - uncurried"
+  )
+
+  t.equals(
+    reduce((acc, next) => acc + next, 0)([1, 2, 3]),
+    6,
+    "Sum an array-curried"
+  )
 
   t.equals(
     reduce((acc, next) => acc + next, 0)(12),
@@ -17,7 +27,7 @@ test("reduce", t => {
   )
 
   t.equals(
-    reduce((acc = 0, next) => acc + next, 0)([]),
+    reduce((acc, next) => acc + next, 0)([]),
     0,
     "Reducing empty array return default acc"
   )