✨ Reduce

Author: UltiRequiem

src/language/for_each.ts

@@ -0,0 +1,13 @@
+export type ForEachCallback<T> = (
+  element: T,
+  index: number,
+  array: readonly T[],
+) => void;
+
+export function forEach<T>(array: T[], callback: ForEachCallback<T>) {
+  const entries = array.entries();
+
+  for (const [index, value] of entries) {
+    callback(value, index, array);
+  }
+}

src/language/reduce.ts

@@ -0,0 +1,28 @@
+export type ReduceCallback<T> = (
+  accumulator: T,
+  value: T,
+  index: number,
+  array: readonly T[],
+) => unknown;
+
+export function reduce<T, F extends ReduceCallback<T>>(
+  array: T[],
+  callback: F,
+  initialValue?: unknown,
+) {
+  const copy = [...array];
+
+  if (array.length >= 1) {
+    initialValue = copy.shift();
+  }
+
+  let previous = initialValue;
+
+  const entries = copy.entries();
+
+  for (const [index, element] of entries) {
+    previous = callback(previous as T, element, index, array);
+  }
+
+  return previous as ReturnType<F>;
+}