From 959c114b0e04b3766fd0f5a9bd6ab6229ef0b141 Mon Sep 17 00:00:00 2001
From: Angelos Chalaris <chalarangelo@gmail.com>
Date: Sun, 29 Nov 2020 12:04:53 +0200
Subject: [PATCH] Update takeWhile snippets

Add takeUntil snippets
---
 snippets/takeRightUntil.md | 24 ++++++++++++++++++++++++
 snippets/takeRightWhile.md | 16 +++++++++++-----
 snippets/takeUntil.md      | 22 ++++++++++++++++++++++
 snippets/takeWhile.md      |  7 ++++---
 4 files changed, 61 insertions(+), 8 deletions(-)
 create mode 100644 snippets/takeRightUntil.md
 create mode 100644 snippets/takeUntil.md

diff --git a/snippets/takeRightUntil.md b/snippets/takeRightUntil.md
new file mode 100644
index 000000000..fd27a35a4
--- /dev/null
+++ b/snippets/takeRightUntil.md
@@ -0,0 +1,24 @@
+---
+title: takeRightUntil
+tags: array,intermediate
+---
+
+Removes elements from the end of an array until the passed function returns `true`.
+Returns the removed elements.
+
+- Create a reversed copy of the array, using the spread operator (`...`) and `Array.prototype.reverse()`.
+- Loop through the reversed copy, using a `for...of` loop over `Array.prototype.entries()` until the returned value from the function is truthy.
+- Return the removed elements, using `Array.prototype.slice()`.
+- The callback function, `fn`, accepts a single argument which is the value of the element.
+
+```js
+const takeRightUntil = (arr, fn) => {
+  for (const [i, val] of [...arr].reverse().entries())
+    if (fn(val)) return i === 0 ? [] : arr.slice(-i);
+  return arr;
+};
+```
+
+```js
+takeRightUntil([1, 2, 3, 4], n => n < 3); // [3, 4]
+```
diff --git a/snippets/takeRightWhile.md b/snippets/takeRightWhile.md
index 66e4646b7..03ff8c342 100644
--- a/snippets/takeRightWhile.md
+++ b/snippets/takeRightWhile.md
@@ -3,16 +3,22 @@ title: takeRightWhile
 tags: array,intermediate
 ---
 
-Removes elements from the end of an array until the passed function returns `true`.
+Removes elements from the end of an array until the passed function returns `false`.
 Returns the removed elements.
 
-- Loop through the array, using `Array.prototype.reduceRight()` and accumulating elements while `func` returns falsy values.
+- Create a reversed copy of the array, using the spread operator (`...`) and `Array.prototype.reverse()`.
+- Loop through the reversed copy, using a `for...of` loop over `Array.prototype.entries()` until the returned value from the function is falsy.
+- Return the removed elements, using `Array.prototype.slice()`.
+- The callback function, `fn`, accepts a single argument which is the value of the element.
 
 ```js
-const takeRightWhile = (arr, func) =>
-  arr.reduceRight((acc, el) => (func(el) ? acc : [el, ...acc]), []);
+const takeRightWhile = (arr, fn) => {
+  for (const [i, val] of [...arr].reverse().entries())
+    if (!fn(val)) return i === 0 ? [] : arr.slice(-i);
+  return arr;
+};
 ```
 
 ```js
-takeRightWhile([1, 2, 3, 4], n => n < 3); // [3, 4]
+takeRightWhile([1, 2, 3, 4], n => n >= 3); // [3, 4]
 ```
diff --git a/snippets/takeUntil.md b/snippets/takeUntil.md
new file mode 100644
index 000000000..093eda2f1
--- /dev/null
+++ b/snippets/takeUntil.md
@@ -0,0 +1,22 @@
+---
+title: takeUntil
+tags: array,intermediate
+---
+
+Removes elements in an array until the passed function returns `true`.
+Returns the removed elements.
+
+- Loop through the array, using a `for...of` loop over `Array.prototype.entries()` until the returned value from the function is truthy.
+- Return the removed elements, using `Array.prototype.slice()`.
+- The callback function, `fn`, accepts a single argument which is the value of the element.
+
+```js
+const takeUntil = (arr, fn) => {
+  for (const [i, val] of arr.entries()) if (fn(val)) return arr.slice(0, i);
+  return arr;
+};
+```
+
+```js
+takeUntil([1, 2, 3, 4], n => n >= 3); // [1, 2]
+```
diff --git a/snippets/takeWhile.md b/snippets/takeWhile.md
index 2177e2071..8aea24ae7 100644
--- a/snippets/takeWhile.md
+++ b/snippets/takeWhile.md
@@ -6,12 +6,13 @@ tags: array,intermediate
 Removes elements in an array until the passed function returns `false`.
 Returns the removed elements.
 
-- Loop through the array, using a `for...of` loop over `Array.prototype.entries()` until the returned value from the function is `false`.
+- Loop through the array, using a `for...of` loop over `Array.prototype.entries()` until the returned value from the function is falsy.
 - Return the removed elements, using `Array.prototype.slice()`.
+- The callback function, `fn`, accepts a single argument which is the value of the element.
 
 ```js
-const takeWhile = (arr, func) => {
-  for (const [i, val] of arr.entries()) if (!func(val)) return arr.slice(0, i);
+const takeWhile = (arr, fn) => {
+  for (const [i, val] of arr.entries()) if (!fn(val)) return arr.slice(0, i);
   return arr;
 };
 ```