From aaafc3299944bd112732942fcd79101cc3efe01b Mon Sep 17 00:00:00 2001 From: 30secondsofcode <30secondsofcode@gmail.com> Date: Sun, 18 Feb 2018 17:47:02 +0000 Subject: [PATCH] Travis build: 1696 --- README.md | 31 +++++++++++++++++++++++++++++++ docs/index.html | 9 ++++++++- 2 files changed, 39 insertions(+), 1 deletion(-) diff --git a/README.md b/README.md index 6bff27e25..bddfc47cd 100644 --- a/README.md +++ b/README.md @@ -157,6 +157,7 @@ average(1, 2, 3); * [`sortedIndexBy`](#sortedindexby) * [`sortedLastIndex`](#sortedlastindex) * [`sortedLastIndexBy`](#sortedlastindexby) +* [`stableSort`](#stablesort-) * [`symmetricDifference`](#symmetricdifference) * [`symmetricDifferenceBy`](#symmetricdifferenceby) * [`symmetricDifferenceWith`](#symmetricdifferencewith) @@ -2328,6 +2329,36 @@ sortedLastIndexBy([{ x: 4 }, { x: 5 }], { x: 4 }, o => o.x); // 1
[⬆ Back to top](#table-of-contents) +### stableSort ![advanced](/advanced.svg) + +Performs stable sorting of an array, preserving the initial indexes of items when their values are the same. +Does not mutate the original array, but returns a new array instead. + +Use `Array.map()` to pair each element of the input array with its corresponding index. +Use `Array.sort()` and a `compare` function to sort the list, preserving their initial order if the items compared are equal. +Use `Array.map()` to convert back to the initial array items. + +```js +const stableSort = (arr, compare) => + arr + .map((item, index) => ({ item, index })) + .sort((a, b) => compare(a.item, b.item) || a.index - b.index) + .map(({ item }) => item); +``` + +
+Examples + +```js +const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]; +const stable = stableSort(arr, () => 0); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10] +``` + +
+ +
[⬆ Back to top](#table-of-contents) + + ### symmetricDifference Returns the symmetric difference between two arrays. diff --git a/docs/index.html b/docs/index.html index 141de6d37..d8b48804d 100644 --- a/docs/index.html +++ b/docs/index.html @@ -50,7 +50,7 @@ scrollToTop(); } }, false); - }

logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.

 

Adapter

ary

Creates a function that accepts up to n arguments, ignoring any additional arguments.

Call the provided function, fn, with up to n arguments, using Array.slice(0,n) and the spread operator (...).

const ary = (fn, n) => (...args) => fn(...args.slice(0, n));
+      }
logo 30 seconds of code Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.
 
Adapter
ary
Creates a function that accepts up to n arguments, ignoring any additional arguments.
Call the provided function, fn, with up to n arguments, using Array.slice(0,n) and the spread operator (...).
const ary = (fn, n) => (...args) => fn(...args.slice(0, n));
 
const firstTwoMax = ary(Math.max, 2);
 [[2, 6, 'a'], [8, 4, 6], [10]].map(x => firstTwoMax(...x)); // [6, 8, 10]
 
call
Given a key and a set of arguments, call them when given a context. Primarily useful in composition.
Use a closure to call a stored key with stored arguments.
const call = (key, ...args) => context => context[key](...args);
@@ -448,6 +448,13 @@ Object.assig
   return index === -1 ? 0 : arr.length - index;
 };
 
sortedLastIndexBy([{ x: 4 }, { x: 5 }], { x: 4 }, o => o.x); // 1
+
stableSortadvanced
Performs stable sorting of an array, preserving the initial indexes of items when their values are the same. Does not mutate the original array, but returns a new array instead.
Use Array.map() to pair each element of the input array with its corresponding index. Use Array.sort() and a compare function to sort the list, preserving their initial order if the items compared are equal. Use Array.map() to convert back to the initial array items.
const stableSort = (arr, compare) =>
+  arr
+    .map((item, index) => ({ item, index }))
+    .sort((a, b) => compare(a.item, b.item) || a.index - b.index)
+    .map(({ item }) => item);
+
const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+const stable = stableSort(arr, () => 0); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
 
symmetricDifference
Returns the symmetric difference between two arrays.
Create a Set from each array, then use Array.filter() on each of them to only keep values not contained in the other.
const symmetricDifference = (a, b) => {
   const sA = new Set(a),
     sB = new Set(b);