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@ -44,6 +44,7 @@
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* [Similarity between arrays](#similarity-between-arrays)
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* [Sum of array of numbers](#sum-of-array-of-numbers)
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* [Tail of list](#tail-of-list)
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* [Take every nth element](#take-every-nth-element)
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* [Take right](#take-right)
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* [Take](#take)
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* [Unique values of array](#unique-values-of-array)
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@ -61,8 +62,9 @@
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### Function
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* [Chain asynchronous functions](#chain-asynchronous-functions)
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* [Compose functions](#compose-functions)
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* [Curry](#curry)
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* [Pipe](#pipe)
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* [Pipe functions](#pipe-functions)
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* [Promisify](#promisify)
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* [Run promises in series](#run-promises-in-series)
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* [Sleep](#sleep)
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@ -85,6 +87,7 @@
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* [Speech synthesis (experimental)](#speech-synthesis-experimental)
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### Node
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* [Read file as array of lines](#read-file-as-array-of-lines)
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* [Write JSON to file](#write-json-to-file)
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### Object
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@ -102,6 +105,7 @@
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* [Truncate a string](#truncate-a-string)
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### Utility
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* [3 digit hexcode to 6 digit hexcode](#3-digit-hexcode-to-6-digit-hexcode)
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* [Escape regular expression](#escape-regular-expression)
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* [Get native type of value](#get-native-type-of-value)
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* [Hexcode to RGB](#hexcode-to-rgb)
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@ -128,11 +132,11 @@
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### Array concatenation
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Use `Array.concat()` to concatenate an array with any additional arrays and/or values, specified in `args`.
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Use Array spread operators (`...`) to concatenate an array with any additional arrays and/or values, specified in `args`.
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```js
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const ArrayConcat = (arr, ...args) => [].concat(arr, ...args);
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// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 2, 3, [4]]
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const ArrayConcat = (arr, ...args) => [...arr,...args];
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// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 1, 2, 3, [4]]
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```
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[⬆ back to top](#table-of-contents)
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@ -213,11 +217,11 @@ const union = (a, b) => Array.from(new Set([...a, ...b]));
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### Array without
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Use `Array.filter()` to create an array excluding all given values.
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Use `Array.filter()` to create an array excluding(using `!Array.includes()`) all given values.
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```js
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const without = (arr, ...args) => arr.filter(v => args.indexOf(v) === -1);
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// without[2, 1, 2, 3], 1, 2) -> [3]
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const without = (arr, ...args) => arr.filter(v => !args.includes(v));
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// without([2, 1, 2, 3], 1, 2) -> [3]
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// without([2, 1, 2, 3, 4, 5, 5, 5, 3, 2, 7, 7], 3, 1, 5, 2) -> [ 4, 7, 7 ]
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```
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@ -231,7 +235,7 @@ If lengths of the argument-arrays vary, `undefined` is used where no value could
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```js
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const zip = (...arrays) => {
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const maxLength = Math.max.apply(null, arrays.map(a => a.length));
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const maxLength = Math.max(...arrays.map(x => x.length));
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return Array.from({length: maxLength}).map((_, i) => {
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return Array.from({length: arrays.length}, (_, k) => arrays[k][i]);
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})
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@ -434,7 +438,7 @@ You can omit `start` to use a default value of `0`.
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```js
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const initializeArrayRange = (end, start = 0) =>
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Array.apply(null, Array(end - start)).map((v, i) => i + start);
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Array.from({ length: end - start }).map((v, i) => i + start);
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// initializeArrayRange(5) -> [0,1,2,3,4]
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```
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@ -551,6 +555,17 @@ const tail = arr => arr.length > 1 ? arr.slice(1) : arr;
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[⬆ back to top](#table-of-contents)
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### Take every nth element
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Use `Array.filter()` to create a new array that contains every nth element of a given array.
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```js
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const everynth = (arr, nth) => arr.filter((e, i) => i % nth === 0);
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// everynth([1,2,3,4,5,6], 2) -> [ 1, 3, 5 ]
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```
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[⬆ back to top](#table-of-contents)
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### Take right
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Use `Array.slice()` to create a slice of the array with `n` elements taken from the end.
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@ -707,6 +722,22 @@ chainAsync([
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[⬆ back to top](#table-of-contents)
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### Compose functions
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Use `Array.reduce()` to perform right-to-left function composition.
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The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
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```js
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const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));
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/*
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const add5 = x => x + 5
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const multiply = (x, y) => x * y
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const multiplyAndAdd5 = compose(add5, multiply)
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multiplyAndAdd5(5, 2) -> 15
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*/
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```
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[⬆ back to top](#table-of-contents)
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### Curry
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Use recursion.
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@ -725,9 +756,9 @@ const curry = (fn, arity = fn.length, ...args) =>
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[⬆ back to top](#table-of-contents)
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### Pipe
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### Pipe functions
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Use `Array.reduce()` to perform left-to-right function composition.
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Use `Array.reduce()` with the spread operator (`...`) to perform left-to-right function composition.
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The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
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```js
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@ -967,6 +998,28 @@ const speak = message => {
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[⬆ back to top](#table-of-contents)
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## Node
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### Read file as array of lines
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Use `readFileSync` function in `fs` node package to create a `Buffer` from a file.
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convert buffer to string using `toString(encoding)` function.
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creating an array from contents of file by `split`ing file content line by line(each `\n`).
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```js
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const fs = require('fs');
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const readFileToArray = filename => fs.readFileSync(filename).toString('UTF8').split('\n');
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/*
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contents of test.txt :
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line1
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line2
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line3
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___________________________
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let arr = readFileToArray('test.txt')
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console.log(arr) // -> ['line1', 'line2', 'line3']
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*/
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```
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[⬆ back to top](#table-of-contents)
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### Write JSON to file
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Use `fs.writeFile()`, template literals and `JSON.stringify()` to write a `json` object to a `.json` file.
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@ -1114,6 +1167,20 @@ const truncate = (str, num) =>
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[⬆ back to top](#table-of-contents)
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## Utility
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### 3-digit hexcode to 6-digit hexcode
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Use `Array.map()`, `split()` and `Array.join()` to join the mapped array for converting a three-digit RGB notated hexadecimal colorcode to the six-digit form.
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```js
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const convertHex = shortHex =>
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shortHex[0] == '#' ? ('#' + shortHex.slice(1).split('').map(x => x+x).join('')) :
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('#' + shortHex.split('').map(x => x+x).join(''));
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// convertHex('#03f') -> '#0033ff'
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// convertHex('05a') -> '#0055aa'
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```
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[⬆ back to top](#table-of-contents)
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### Escape regular expression
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Use `replace()` to escape special characters.
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Angelos Chalaris