diff --git a/README.md b/README.md index 7160b9afb..b8412a802 100644 --- a/README.md +++ b/README.md @@ -13,7 +13,10 @@ * [Array concatenation](#array-concatenation) * [Array difference](#array-difference) * [Array intersection](#array-intersection) +* [Array sample](#array-sample) * [Array union](#array-union) +* [Array without](#array-without) +* [Array zip](#array-zip) * [Average of array of numbers](#average-of-array-of-numbers) * [Chunk array](#chunk-array) * [Compact](#compact) @@ -39,6 +42,7 @@ * [Similarity between arrays](#similarity-between-arrays) * [Sum of array of numbers](#sum-of-array-of-numbers) * [Tail of list](#tail-of-list) +* [Take right](#take-right) * [Take](#take) * [Unique values of array](#unique-values-of-array) @@ -149,6 +153,18 @@ const intersection = (a, b) => { const s = new Set(b); return a.filter(x => s.ha [⬆ back to top](#table-of-contents) +### Array sample + +Use `Math.random()` to generate a random number, multiply it with `length` and round it of to the nearest whole number using `Math.floor()`. +This method also works with strings. + +```js +const sample = arr => arr[Math.floor(Math.random() * arr.length)]; +// sample([3, 7, 9, 11]) -> 9 +``` + +[⬆ back to top](#table-of-contents) + ### Array union Create a `Set` with all values of `a` and `b` and convert to an array. @@ -160,6 +176,37 @@ const union = (a, b) => Array.from(new Set([...a, ...b])); [⬆ back to top](#table-of-contents) +### Array without + +Use `Array.filter()` to create an array excluding all given values. + +```js +const without = (arr, ...args) => arr.filter(v => args.indexOf(v) === -1); +// without[2, 1, 2, 3], 1, 2) -> [3] +// without([2, 1, 2, 3, 4, 5, 5, 5, 3, 2, 7, 7], 3, 1, 5, 2) -> [ 4, 7, 7 ] +``` + +[⬆ back to top](#table-of-contents) + +### Array zip + +Use `Math.max.apply()` to get the longest array in the arguments. +Creates an array with that length as return value and use `Array.from()` with a map-function to create an array of grouped elements. +If lengths of the argument-arrays vary, `undefined` is used where no value could be found. + +```js +const zip = (...arrays) => { + const maxLength = Math.max.apply(null, arrays.map(a => a.length)); + return Array.from({length: maxLength}).map((_, i) => { + return Array.from({length: arrays.length}, (_, k) => arrays[k][i]); + }) +} +//zip(['a', 'b'], [1, 2], [true, false]); -> [['a', 1, true], ['b', 2, false]] +//zip(['a'], [1, 2], [true, false]); -> [['a', 1, true], [undefined, 2, false]] +``` + +[⬆ back to top](#table-of-contents) + ### Average of array of numbers Use `Array.reduce()` to add each value to an accumulator, initialized with a value of `0`, divide by the `length` of the array. @@ -180,7 +227,7 @@ If the original array can't be split evenly, the final chunk will contain the re ```js const chunk = (arr, size) => Array.from({length: Math.ceil(arr.length / size)}, (v, i) => arr.slice(i * size, i * size + size)); -// chunk([1,2,3,4,5], 2) -> [[1,2],[3,4],5] +// chunk([1,2,3,4,5], 2) -> [[1,2],[3,4],[5]] ``` [⬆ back to top](#table-of-contents) @@ -210,11 +257,11 @@ const countOccurrences = (arr, value) => arr.reduce((a, v) => v === value ? a + ### Deep flatten array Use recursion. -Use `Array.reduce()` to get all elements that are not arrays, flatten each element that is an array. +Use `Array.concat()` with an empty array (`[]`) and the spread operator (`...`) to flatten an array. +Rrecursively flatten each element that is an array. ```js -const deepFlatten = arr => - arr.reduce((a, v) => a.concat(Array.isArray(v) ? deepFlatten(v) : v), []); +const deepFlatten = arr => [].concat(...arr.map(v => Array.isArray(v) ? deepFlatten(v) : v)); // deepFlatten([1,[2],[[3],4],5]) -> [1,2,3,4,5] ``` @@ -469,6 +516,18 @@ const tail = arr => arr.length > 1 ? arr.slice(1) : arr; [⬆ back to top](#table-of-contents) +### Take right + +Use `Array.slice()` to create a slice of the array with `n` elements taken from the end. + +```js +const takeRight = (arr, n = 1) => arr.slice(arr.length - n, arr.length); +// takeRight([1, 2, 3], 2) -> [ 2, 3 ] +// takeRight([1, 2, 3]) -> [3] +``` + +[⬆ back to top](#table-of-contents) + ### Take Use `Array.slice()` to create a slice of the array with `n` elements taken from the beginning. @@ -633,11 +692,17 @@ const curry = (fn, arity = fn.length, ...args) => ### Pipe -Use `Array.reduce()` to pass value through functions. +Use `Array.reduce()` to perform left-to-right function composition. +The first (leftmost) function can accept one or more arguments; the remaining functions must be unary. ```js -const pipe = (...funcs) => arg => funcs.reduce((acc, func) => func(acc), arg); -// pipe(btoa, x => x.toUpperCase())("Test") -> "VGVZDA==" +const pipe = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args))); +/* +const add5 = x => x + 5 +const multiply = (x, y) => x * y +const multiplyAndAdd5 = pipe(multiply, add5) +multiplyAndAdd5(5, 2) -> 15 +*/ ``` [⬆ back to top](#table-of-contents) diff --git a/snippets/array-sample.md b/snippets/array-sample.md index d48f13840..9de5c5ae0 100644 --- a/snippets/array-sample.md +++ b/snippets/array-sample.md @@ -1,9 +1,9 @@ ### Array sample -Use `Math.random()` to generate a random number, multiply it with `Array.length` and round it of to the nearest whole number using `Math.floor()`. Works with strings too. +Use `Math.random()` to generate a random number, multiply it with `length` and round it of to the nearest whole number using `Math.floor()`. +This method also works with strings. ```js const sample = arr => arr[Math.floor(Math.random() * arr.length)]; - -// sample([3, 7, 9, 11]) -> 9 -``` \ No newline at end of file +// sample([3, 7, 9, 11]) -> 9 +``` diff --git a/snippets/without.md b/snippets/array-without.md similarity index 88% rename from snippets/without.md rename to snippets/array-without.md index 00876b5c9..dd657fe2a 100644 --- a/snippets/without.md +++ b/snippets/array-without.md @@ -1,12 +1,9 @@ -### Without +### Array without -Use `Array.filter()` to create an array excluding all given values +Use `Array.filter()` to create an array excluding all given values. ```js - -const without = (arr, ...args) => arr.filter(v => args.indexOf(v) === -1) - +const without = (arr, ...args) => arr.filter(v => args.indexOf(v) === -1); // without[2, 1, 2, 3], 1, 2) -> [3] // without([2, 1, 2, 3, 4, 5, 5, 5, 3, 2, 7, 7], 3, 1, 5, 2) -> [ 4, 7, 7 ] - ``` diff --git a/snippets/array-zip.md b/snippets/array-zip.md index 08c40ed68..6c9a2491b 100644 --- a/snippets/array-zip.md +++ b/snippets/array-zip.md @@ -1,17 +1,16 @@ ### Array zip -Use `Math.max.apply` to get the longest array in the arguments. -Creates an array with that length as return value and use `Array.from` with a map-function to create an array of grouped elements. +Use `Math.max.apply()` to get the longest array in the arguments. +Creates an array with that length as return value and use `Array.from()` with a map-function to create an array of grouped elements. If lengths of the argument-arrays vary, `undefined` is used where no value could be found. ```js const zip = (...arrays) => { const maxLength = Math.max.apply(null, arrays.map(a => a.length)); return Array.from({length: maxLength}).map((_, i) => { - return Array.from({length: arrays.length}, (_, k) => arrays[k][i]) + return Array.from({length: arrays.length}, (_, k) => arrays[k][i]); }) } - //zip(['a', 'b'], [1, 2], [true, false]); -> [['a', 1, true], ['b', 2, false]] //zip(['a'], [1, 2], [true, false]); -> [['a', 1, true], [undefined, 2, false]] ``` diff --git a/snippets/deep-flatten-array.md b/snippets/deep-flatten-array.md index 1dffe860f..d33ff7e25 100644 --- a/snippets/deep-flatten-array.md +++ b/snippets/deep-flatten-array.md @@ -1,7 +1,8 @@ ### Deep flatten array Use recursion. -Use `[].concat()` and the spread operator `...` to flatten an array, and recursively flatten each element that is an array. +Use `Array.concat()` with an empty array (`[]`) and the spread operator (`...`) to flatten an array. +Rrecursively flatten each element that is an array. ```js const deepFlatten = arr => [].concat(...arr.map(v => Array.isArray(v) ? deepFlatten(v) : v)); diff --git a/snippets/pipe.md b/snippets/pipe.md index f46a32148..e5136777b 100644 --- a/snippets/pipe.md +++ b/snippets/pipe.md @@ -1,15 +1,14 @@ ### Pipe -Use `Array.reduce()` to perform left-to-right function composition. The first (leftmost) function can accept one or more arguments; the remaining functions must be unary. +Use `Array.reduce()` to perform left-to-right function composition. +The first (leftmost) function can accept one or more arguments; the remaining functions must be unary. ```js -const pipe = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args))) +const pipe = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args))); /* const add5 = x => x + 5 -const multiply = (x, y) => x * y - +const multiply = (x, y) => x * y const multiplyAndAdd5 = pipe(multiply, add5) - multiplyAndAdd5(5, 2) -> 15 */ ``` diff --git a/snippets/takeRight.md b/snippets/take-right.md similarity index 83% rename from snippets/takeRight.md rename to snippets/take-right.md index 03fc634fa..1e7c55766 100644 --- a/snippets/takeRight.md +++ b/snippets/take-right.md @@ -1,4 +1,4 @@ -### takeRight +### Take right Use `Array.slice()` to create a slice of the array with `n` elements taken from the end. @@ -6,5 +6,4 @@ Use `Array.slice()` to create a slice of the array with `n` elements taken from const takeRight = (arr, n = 1) => arr.slice(arr.length - n, arr.length); // takeRight([1, 2, 3], 2) -> [ 2, 3 ] // takeRight([1, 2, 3]) -> [3] -// takeRight([1, 2, 3]) -> [] -``` \ No newline at end of file +``` diff --git a/tag_database b/tag_database index d1733c293..7e20b7516 100644 --- a/tag_database +++ b/tag_database @@ -2,7 +2,10 @@ anagrams-of-string-(with-duplicates):string array-concatenation:array array-difference:array array-intersection:array +array-sample:array array-union:array +array-without:array +array-zip:array average-of-array-of-numbers:array bottom-visible:browser capitalize-first-letter-of-every-word:string @@ -77,8 +80,8 @@ standard-deviation:math sum-of-array-of-numbers:array swap-values-of-two-variables:utility tail-of-list:array +take-right:array take:array -takeRight:array truncate-a-string:string unique-values-of-array:array URL-parameters:utility @@ -86,4 +89,3 @@ UUID-generator:utility validate-email:utility validate-number:utility value-or-default:utility -without:array