From 657d135e6d173b4e60a6b003d004b38dd76d3b05 Mon Sep 17 00:00:00 2001
From: Anthony Fu <anthonyfu117@hotmail.com>
Date: Wed, 28 Apr 2021 18:15:49 +0800
Subject: [PATCH] feat(array): range

---
 src/array.test.ts |  9 ++++++-
 src/array.ts      | 64 ++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 68 insertions(+), 5 deletions(-)

diff --git a/src/array.test.ts b/src/array.test.ts
index cc7a37a..5103120 100644
--- a/src/array.test.ts
+++ b/src/array.test.ts
@@ -1,4 +1,4 @@
-import { flattenArrayable } from './array'
+import { flattenArrayable, range } from './array'
 
 it('flattenArrayable', () => {
   expect(flattenArrayable()).toEqual([])
@@ -8,3 +8,10 @@ it('flattenArrayable', () => {
   expect(flattenArrayable([1, [1, 2]])).toEqual([1, 1, 2])
   expect(flattenArrayable([1, [1, [2]]])).toEqual([1, 1, [2]])
 })
+
+it('range', () => {
+  expect(range(0)).toEqual([])
+  expect(range(2)).toEqual([0, 1])
+  expect(range(2, 5)).toEqual([2, 3, 4])
+  expect(range(2, 10, 2)).toEqual([2, 4, 6, 8])
+})
diff --git a/src/array.ts b/src/array.ts
index 967a0b3..4ca20a1 100644
--- a/src/array.ts
+++ b/src/array.ts
@@ -1,7 +1,9 @@
 import { Arrayable, Nullable } from './types'
 
 /**
- * Convert Arrayable<T> to Array<T>
+ * Convert `Arrayable<T>` to `Array<T>`
+ *
+ * @category Array
  */
 export function toArray<T>(array?: Nullable<Arrayable<T>>): Array<T> {
   array = array || []
@@ -11,7 +13,9 @@ export function toArray<T>(array?: Nullable<Arrayable<T>>): Array<T> {
 }
 
 /**
- * Convert Arrayable<T> to Array<T>
+ * Convert `Arrayable<T>` to `Array<T>` and flat it
+ *
+ * @category Array
  */
 export function flattenArrayable<T>(array?: Nullable<Arrayable<T | Array<T>>>): Array<T> {
   return toArray(array).flat(1) as Array<T>
@@ -19,6 +23,8 @@ export function flattenArrayable<T>(array?: Nullable<Arrayable<T | Array<T>>>):
 
 /**
  * Use rest arguments to merge arrays
+ *
+ * @category Array
  */
 export function mergeArrayable<T>(...args: Nullable<Arrayable<T>>[]): Array<T> {
   return args.flatMap(i => toArray(i))
@@ -27,6 +33,7 @@ export function mergeArrayable<T>(...args: Nullable<Arrayable<T>>[]): Array<T> {
 /**
  * Divide an array into two parts by a filter function.
  *
+ * @category Array
  * @example const [odd, even] = partition([1, 2, 3, 4], i => i % 2 != 0)
  */
 export function partition<T>(array: readonly T[], filter: (i: T, idx: number, arr: readonly T[]) => any) {
@@ -36,17 +43,34 @@ export function partition<T>(array: readonly T[], filter: (i: T, idx: number, ar
   return [pass, fail]
 }
 
+/**
+ * Unique an Array
+ *
+ * @category Array
+ */
 export function uniq<T>(array: readonly T[]): T[] {
   return Array.from(new Set(array))
 }
 
+/**
+ * Get last item
+ *
+ * @category Array
+ */
 export function last(array: readonly []): undefined
 export function last<T>(array: readonly T[]): T
 export function last<T>(array: readonly T[]): T | undefined {
   return at(array, -1)
 }
 
+/**
+ * Remove an item from Array
+ *
+ * @category Array
+ */
 export function remove<T>(array: T[], value: T) {
+  if (!array)
+    return false
   const index = array.indexOf(value)
   if (index >= 0) {
     array.splice(index, 1)
@@ -55,6 +79,11 @@ export function remove<T>(array: T[], value: T) {
   return false
 }
 
+/**
+ * Get nth item of Array. Negative for backward
+ *
+ * @category Array
+ */
 export function at(array: readonly [], index: number): undefined
 export function at<T>(array: readonly T[], index: number): T
 export function at<T>(array: readonly T[] | [], index: number): T | undefined {
@@ -62,10 +91,37 @@ export function at<T>(array: readonly T[] | [], index: number): T | undefined {
   if (!len)
     return undefined
 
-  index = index % len
-
   if (index < 0)
     index += len
 
   return array[index]
 }
+
+/**
+ * Genrate a range array of numbers. The `stop` is exclusive.
+ *
+ * @category Array
+ */
+export function range(stop: number): number[]
+export function range(start: number, stop: number, step?: number): number[]
+export function range(...args: any): number[] {
+  let start: number, stop: number, step: number
+
+  if (args.length === 1) {
+    start = 0
+    step = 1;
+    ([stop] = args)
+  }
+  else {
+    ([start, stop, step = 1] = args)
+  }
+
+  const arr: number[] = []
+  let current = start
+  while (current < stop) {
+    arr.push(current)
+    current += step || 1
+  }
+
+  return arr
+}