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Angelos Chalaris
2018-01-03 17:02:01 +02:00
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@ -5,7 +5,7 @@
[![License](https://img.shields.io/badge/license-CC0--1.0-blue.svg)](https://github.com/Chalarangelo/30-seconds-of-code/blob/master/LICENSE) [![Gitter chat](https://img.shields.io/badge/chat-on%20gitter-4FB999.svg)](https://gitter.im/30-seconds-of-code/Lobby) [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg)](http://makeapullrequest.com) [![Travis Build](https://travis-ci.org/Chalarangelo/30-seconds-of-code.svg?branch=master)](https://travis-ci.org/Chalarangelo/30-seconds-of-code) [![Insight.io](https://img.shields.io/badge/insight.io-Ready-brightgreen.svg)](https://insight.io/github.com/Chalarangelo/30-seconds-of-code/tree/master/?source=0) [![js-semistandard-style](https://img.shields.io/badge/code%20style-semistandard-brightgreen.svg)](https://github.com/Flet/semistandard) [![ProductHunt](https://img.shields.io/badge/producthunt-vote-orange.svg)](https://www.producthunt.com/posts/30-seconds-of-code)
> Curated collection of useful Javascript snippets that you can understand in 30 seconds or less.
> Curated collection of useful JavaScript snippets that you can understand in 30 seconds or less.
- Use <kbd>Ctrl</kbd> + <kbd>F</kbd> or <kbd>command</kbd> + <kbd>F</kbd> to search for a snippet.
@ -13,7 +13,58 @@
- Snippets are written in ES6, use the [Babel transpiler](https://babeljs.io/) to ensure backwards-compatibility.
- You can import these snippets into your text editor of choice (VSCode, Atom, Sublime) using the files found in [this repo](https://github.com/Rob-Rychs/30-seconds-of-code-texteditorsnippets).
- You can import these snippets into Alfred 3, using [this file](https://github.com/lslvxy/30-seconds-of-code-alfredsnippets).
- You can find a package with all the snippets on [npm](https://www.npmjs.com/package/30-seconds-of-code). Bear in mind that most of these snippets are not production-ready.
#### Package
⚠️ **WARNING:** Snippets are not production ready.
You can find a package with all the snippets on [npm](https://www.npmjs.com/package/30-seconds-of-code).
```
npm install 30-seconds-of-code
```
CDN links
- [ES2017 Full (UMD)](https://unpkg.com/30-seconds-of-code)
- [ES5 Minified (UMD)](https://unpkg.com/30-seconds-of-code/dist/_30s.es5.min.js)
<details>
**Browser**
> IMPORTANT: replace the `src` with the full version link and desired target spec (such as ES5 minified)):
```html
<script src="https://unpkg.com/30-seconds-of-code"></script>
<script>
_30s.average(1, 2, 3);
</script>
```
**Node**
```js
// CommonJS
const _30s = require('30-seconds-of-code');
_30s.average(1, 2, 3);
// ES Modules
import _30s from '30-seconds-of-code';
_30s.average(1, 2, 3);
```
To import snippets directly:
```js
// CommonJS
const { average } = require('30-seconds-of-code');
average(1, 2, 3);
// ES Modules
import { average } from '30-seconds-of-code';
average(1, 2, 3);
```
</details>
## Table of Contents
@ -60,6 +111,8 @@
* [`join`](#join)
* [`last`](#last)
* [`mapObject`](#mapobject)
* [`maxN`](#maxn)
* [`minN`](#minn)
* [`nthElement`](#nthelement)
* [`pick`](#pick)
* [`pull`](#pull)
@ -162,11 +215,14 @@
* [`distance`](#distance)
* [`elo`](#elo)
* [`factorial`](#factorial)
* [`factors`](#factors)
* [`fibonacci`](#fibonacci)
* [`fibonacciCountUntilNum`](#fibonaccicountuntilnum)
* [`fibonacciUntilNum`](#fibonacciuntilnum)
* [`gcd`](#gcd)
* [`geometricProgression`](#geometricprogression)
* [`hammingDistance`](#hammingdistance)
* [`howManyTimes`](#howmanytimes)
* [`inRange`](#inrange)
* [`isArmstrongNumber`](#isarmstrongnumber)
* [`isDivisible`](#isdivisible)
@ -237,6 +293,7 @@
* [`isAbsoluteURL`](#isabsoluteurl)
* [`mask`](#mask)
* [`palindrome`](#palindrome)
* [`pluralize`](#pluralize)
* [`repeatString`](#repeatstring)
* [`reverseString`](#reversestring)
* [`sortCharactersInString`](#sortcharactersinstring)
@ -290,23 +347,24 @@
<details>
<summary>View contents</summary>
* [`geometricProgression`](#geometricprogression)
* [`maxN`](#maxn)
* [`minN`](#minn)
</details>
---
## 🔌 Adapter
### 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.
### 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.
```js
const call = (key, ...args) => context => context[key](...args);
```
```
<details>
<summary>Examples</summary>
@ -318,23 +376,23 @@ const map = call.bind(null, 'map');
Promise.resolve([1, 2, 3])
.then(map(x => 2 * x))
.then(console.log); //[ 2, 4, 6 ]
```
```
</details>
<br>[⬆ Back to top](#table-of-contents)
### collectInto
Changes a function that accepts an array into a variadic function.
Given a function, return a closure that collects all inputs into an array-accepting function.
### collectInto
Changes a function that accepts an array into a variadic function.
Given a function, return a closure that collects all inputs into an array-accepting function.
```js
const collectInto = fn => (...args) => fn(args);
```
```
<details>
<summary>Examples</summary>
@ -344,23 +402,23 @@ let p1 = Promise.resolve(1);
let p2 = Promise.resolve(2);
let p3 = new Promise(resolve => setTimeout(resolve, 2000, 3));
Pall(p1, p2, p3).then(console.log);
```
```
</details>
<br>[⬆ Back to top](#table-of-contents)
### flip
Flip takes a function as an argument, then makes the first argument the last
Return a closure that takes variadic inputs, and splices the last argument to make it the first argument before applying the rest.
### flip
Flip takes a function as an argument, then makes the first argument the last
Return a closure that takes variadic inputs, and splices the last argument to make it the first argument before applying the rest.
```js
const flip = fn => (...args) => fn(args.pop(), ...args);
```
```
<details>
<summary>Examples</summary>
@ -372,7 +430,7 @@ let mergePerson = mergeFrom.bind(null, a);
mergePerson(b); // == b
b = {};
Object.assign(b, a); // == b
```
```
</details>
@ -434,16 +492,16 @@ delay(2000).then(() => console.log('Hi!')); // // Promise resolves after 2s
<br>[⬆ Back to top](#table-of-contents)
### spreadOver
Takes a variadic function and returns a closure that accepts an array of arguments to map to the inputs of the function.
Use closures and the spread operator (`...`) to map the array of arguments to the inputs of the function.
### spreadOver
Takes a variadic function and returns a closure that accepts an array of arguments to map to the inputs of the function.
Use closures and the spread operator (`...`) to map the array of arguments to the inputs of the function.
```js
const spreadOver = fn => argsArr => fn(...argsArr);
```
```
<details>
<summary>Examples</summary>
@ -451,7 +509,7 @@ const spreadOver = fn => argsArr => fn(...argsArr);
const arrayMax = spreadOver(Math.max);
arrayMax([1, 2, 3]); // 3
arrayMax([1, 2, 4]); // 4
```
```
</details>
@ -1054,6 +1112,57 @@ squareIt([1, 2, 3]); // { 1: 1, 2: 4, 3: 9 }
<br>[⬆ Back to top](#table-of-contents)
### maxN
Returns the `n` maximum elements from the provided array. If `n` is greater than or equal to the provided array's length, then return the original array(sorted in descending order).
Use `Array.sort()` combined with the spread operator (`...`) to create a shallow clone of the array and sort it in descending order.
Use `Array.slice()` to get the specified number of elements.
Omit the second argument, `n`, to get a one-element array.
```js
const maxN = (arr, n = 1) => [...arr].sort((a, b) => b - a).slice(0, n);
```
<details>
<summary>Examples</summary>
```js
maxN([1, 2, 3]); // [3]
maxN([1, 2, 3], 2); // [3,2]
maxN([1, 2, 3], 4); // [3,2,1]
```
</details>
<br>[⬆ Back to top](#table-of-contents)
### minN
Returns the `n` minimum elements from the provided array. If `n` is greater than or equal to the provided array's length, then return the original array(sorted in ascending order).
Use `Array.sort()` combined with the spread operator (`...`) to create a shallow clone of the array and sort it in ascending order.
Use `Array.slice()` to get the specified number of elements.
Omit the second argument, `n`, to get a one-element array.
```js
const minN = (arr, n = 1) => [...arr].sort((a, b) => a - b).slice(0, n);
```
<details>
<summary>Examples</summary>
```js
minN([1, 2, 3]); // [1]
minN([1, 2, 3], 2); // [1,2]
minN([1, 2, 3], 4); // [1,2,3]
```
</details>
<br>[⬆ Back to top](#table-of-contents)
### nthElement
Returns the nth element of an array.
@ -2763,6 +2872,57 @@ factorial(6); // 720
<br>[⬆ Back to top](#table-of-contents)
### factors
Returns the array of factors of the given `num`.
If the second argument is set to `true` returns only the prime factors of `num`.
If `num` is `1` or `0` returns an empty array.
If `num` is less than `0` returns all the factors of `-int` together with their additive inverses.
Use `Array.from()`, `Array.map()` and `Array.filter()` to find all the factors of `num`.
If given `num` is negative, use `Array.reduce()` to add the additive inverses to the array.
Return all results if `primes` is `false`, else determine and return only the prime factors using `isPrime` and `Array.filter()`.
Omit the second argument, `primes`, to return prime and non-prime factors by default.
**Note**:- _Negative numbers are not considered prime._
```js
const factors = (num, primes = false) => {
const isPrime = num => {
const boundary = Math.floor(Math.sqrt(num));
for (var i = 2; i <= boundary; i++) if (num % i === 0) return false;
return num >= 2;
};
const isNeg = num < 0;
num = isNeg ? -num : num;
let array = Array.from({ length: num - 1 })
.map((val, i) => (num % (i + 2) === 0 ? i + 2 : false))
.filter(val => val);
if (isNeg)
array = array.reduce((acc, val) => {
acc.push(val);
acc.push(-val);
return acc;
}, []);
return primes ? array.filter(isPrime) : array;
};
```
<details>
<summary>Examples</summary>
```js
factors(12); // [2,3,4,6,12]
factors(12, true); // [2,3]
factors(-12); // [2, -2, 3, -3, 4, -4, 6, -6, 12, -12]
factors(-12, true); // [2,3]
```
</details>
<br>[⬆ Back to top](#table-of-contents)
### fibonacci
Generates an array, containing the Fibonacci sequence, up until the nth term.
@ -2871,6 +3031,37 @@ gcd(8, 36); // 4
<br>[⬆ Back to top](#table-of-contents)
### geometricProgression
Initializes an array containing the numbers in the specified range where `start` and `end` are inclusive and the ratio between two terms is `step`.
Returns an error if `step` equals `1`.
Use `Array.from()`, `Math.log()` and `Math.floor()` to create an array of the desired length, `Array.map()` to fill with the desired values in a range.
Omit the second argument, `start`, to use a default value of `1`.
Omit the third argument, `step`, to use a default value of `2`.
```js
const geometricProgression = (end, start = 1, step = 2) =>
Array.from({ length: Math.floor(Math.log(end / start) / Math.log(step)) + 1 }).map(
(v, i) => start * step ** i
);
```
<details>
<summary>Examples</summary>
```js
geometricProgression(256); // [1, 2, 4, 8, 16, 32, 64, 128, 256]
geometricProgression(256, 3); //[3, 6, 12, 24, 48, 96, 192]
geometricProgression(256, 1, 4); //[1, 4, 16, 64, 256]
geometricProgression(256, 2, 1); //Gives error
```
</details>
<br>[⬆ Back to top](#table-of-contents)
### hammingDistance
Calculates the Hamming distance between two values.
@ -2894,6 +3085,47 @@ hammingDistance(2, 3); // 1
<br>[⬆ Back to top](#table-of-contents)
### howManyTimes
Returns the number of times `num` can be divided by `divisor` (integer or fractional) without getting a fractional answer.
Works for both negative and positive integers.
If `divisor` is `-1` or `1` return `Infinity`.
If `divisor` is `-0` or `0` return `0`.
Otherwise, keep dividing `num` with `divisor` and incrementing `i`, while the result is an integer.
Return the number of times the loop was executed, `i`.
```js
const howManyTimes = (num, divisor) => {
if (divisor === 1 || divisor === -1) return Infinity;
if (divisor === 0) return 0;
let i = 0;
while (Number.isInteger(num / divisor)) {
i++;
num = num / divisor;
}
return i;
};
```
<details>
<summary>Examples</summary>
```js
howManyTimes(100, 2); //2
howManyTimes(100, -2); //2
howManyTimes(100, 2.5); //2
howManyTimes(100, 3); //0
howManyTimes(100, 0); //0
howManyTimes(100, 1); //Infinity
howManyTimes(100, -1); //Infinity
```
</details>
<br>[⬆ Back to top](#table-of-contents)
### inRange
Checks if the given number falls within the given range.
@ -4146,6 +4378,38 @@ palindrome('taco cat'); // true
<br>[⬆ Back to top](#table-of-contents)
# pluralize
If `num` is greater than `1` returns the plural form of the given string, else return the singular form.
Check if `num` is greater than `0`. Throw an appropriate `Error` if not, return the appropriate string otherwise.
Omit the third argument, `items`, to use a default plural form same as `item` suffixed with a single `'s'`.
```js
const pluralize = (num, item, items = item + 's') =>
num <= 0
? (() => {
throw new Error(`'num' should be >= 1. Value povided was ${num}.`);
})()
: num === 1 ? item : items;
```
<details>
<summary>Examples</summary>
```js
pluralize(1, 'apple', 'apples'); // 'apple'
pluralize(3, 'apple', 'apples'); // 'apples'
pluralize(2, 'apple'); // 'apples'
pluralize(0, 'apple', 'apples'); // Gives error
pluralize(-3, 'apple', 'apples'); // Gives error
```
</details>
<br>[⬆ Back to top](#table-of-contents)
### repeatString
Repeats a string n times using `String.repeat()`
@ -5145,30 +5409,41 @@ yesNo('Foo', true); // true
<br>[⬆ Back to top](#table-of-contents)
---
## _Uncategorized_
### geometricProgression
### maxN
Initializes an array containing the numbers in the specified range where `start` and `end` are inclusive and the ratio between two terms is `step`.
Returns an error if `step` equals `1`.
Returns the `n` maximum elements from the provided array. If `n` is greater than or equal to the provided array's length than return the original array(sorted in descending order).
Use `Array.from()`, `Math.log()` and `Math.floor()` to create an array of the desired length, `Array.map()` to fill with the desired values in a range.
Omit the second argument, `start`, to use a default value of `1`.
Omit the third argument, `step`, to use a default value of `2`.
Sort's the array's shallow copy in descending order and returns the first n elements
Skip the second argument to get a single element(in the form of a array)
```js
const geometricProgression = (end, start = 1, step = 2) =>
Array.from({ length: Math.floor(Math.log(end / start) / Math.log(step)) + 1 }).map(
(v, i) => start * step ** i
);
const maxN = (arr, n = 1) => [...arr].sort((a, b) => b - a).slice(0, n);
```
```js
geometricProgression(256); // [1, 2, 4, 8, 16, 32, 64, 128, 256]
geometricProgression(256, 3); //[3, 6, 12, 24, 48, 96, 192]
geometricProgression(256, 1, 4); //[1, 4, 16, 64, 256]
geometricProgression(256, 2, 1); //Gives error
maxN([1, 2, 3]); // [3]
maxN([1, 2, 3], 2); // [3,2]
maxN([1, 2, 3], 4); // [3,2,1]
```
<br>[⬆ back to top](#table-of-contents)
### minN
Returns the `n` minimum elements from the provided array. If `n` is greater than or equal to the provided array's length than return the original array(sorted in ascending order).
Sort's the array's shallow copy in ascending order and returns the first n elements
Skip the second argument to get a single element(in the form of a array)
```js
const minN = (arr, n = 1) => [...arr].sort((a, b) => a - b).slice(0, n);
```
```js
minN([1, 2, 3]); // [1]
minN([1, 2, 3], 2); // [1,2]
minN([1, 2, 3], 4); // [1,2,3]
```
<br>[⬆ back to top](#table-of-contents)