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Angelos Chalaris
2017-12-16 14:31:04 +02:00
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@ -44,6 +44,7 @@
* [Similarity between arrays](#similarity-between-arrays)
* [Sum of array of numbers](#sum-of-array-of-numbers)
* [Tail of list](#tail-of-list)
* [Take every nth element](#take-every-nth-element)
* [Take right](#take-right)
* [Take](#take)
* [Unique values of array](#unique-values-of-array)
@ -61,8 +62,9 @@
### Function
* [Chain asynchronous functions](#chain-asynchronous-functions)
* [Compose functions](#compose-functions)
* [Curry](#curry)
* [Pipe](#pipe)
* [Pipe functions](#pipe-functions)
* [Promisify](#promisify)
* [Run promises in series](#run-promises-in-series)
* [Sleep](#sleep)
@ -85,9 +87,11 @@
* [Speech synthesis (experimental)](#speech-synthesis-experimental)
### Node
* [Write json to file](#write-json-to-file)
* [Read file as array of lines](#read-file-as-array-of-lines)
* [Write JSON to file](#write-json-to-file)
### Object
* [Clean JSON object](#clean-json-object)
* [Object from key value pairs](#object-from-key-value-pairs)
* [Object to key value pairs](#object-to-key-value-pairs)
* [Shallow clone object](#shallow-clone-object)
@ -102,6 +106,7 @@
* [Truncate a string](#truncate-a-string)
### Utility
* [3 digit hexcode to 6 digit hexcode](#3-digit-hexcode-to-6-digit-hexcode)
* [Escape regular expression](#escape-regular-expression)
* [Get native type of value](#get-native-type-of-value)
* [Hexcode to RGB](#hexcode-to-rgb)
@ -117,7 +122,6 @@
* [Random integer in range](#random-integer-in-range)
* [Random number in range](#random-number-in-range)
* [RGB to hexadecimal](#rgb-to-hexadecimal)
* [Swap values of two variables](#swap-values-of-two-variables)
* [URL parameters](#url-parameters)
* [UUID generator](#uuid-generator)
* [Validate email](#validate-email)
@ -128,11 +132,11 @@
### Array concatenation
Use `Array.concat()` to concatenate an array with any additional arrays and/or values, specified in `args`.
Use Array spread operators (`...`) to concatenate an array with any additional arrays and/or values, specified in `args`.
```js
const ArrayConcat = (arr, ...args) => [].concat(arr, ...args);
// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 2, 3, [4]]
const ArrayConcat = (arr, ...args) => [...arr,...args];
// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 1, 2, 3, [4]]
```
[⬆ back to top](#table-of-contents)
@ -213,11 +217,11 @@ const union = (a, b) => Array.from(new Set([...a, ...b]));
### Array without
Use `Array.filter()` to create an array excluding all given values.
Use `Array.filter()` to create an array excluding(using `!Array.includes()`) all given values.
```js
const without = (arr, ...args) => arr.filter(v => args.indexOf(v) === -1);
// without[2, 1, 2, 3], 1, 2) -> [3]
const without = (arr, ...args) => arr.filter(v => !args.includes(v));
// 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 ]
```
@ -231,7 +235,7 @@ If lengths of the argument-arrays vary, `undefined` is used where no value could
```js
const zip = (...arrays) => {
const maxLength = Math.max.apply(null, arrays.map(a => a.length));
const maxLength = Math.max(...arrays.map(x => x.length));
return Array.from({length: maxLength}).map((_, i) => {
return Array.from({length: arrays.length}, (_, k) => arrays[k][i]);
})
@ -434,7 +438,7 @@ You can omit `start` to use a default value of `0`.
```js
const initializeArrayRange = (end, start = 0) =>
Array.apply(null, Array(end - start)).map((v, i) => i + start);
Array.from({ length: end - start }).map((v, i) => i + start);
// initializeArrayRange(5) -> [0,1,2,3,4]
```
@ -551,6 +555,17 @@ const tail = arr => arr.length > 1 ? arr.slice(1) : arr;
[⬆ back to top](#table-of-contents)
### Take every nth element
Use `Array.filter()` to create a new array that contains every nth element of a given array.
```js
const everynth = (arr, nth) => arr.filter((e, i) => i % nth === 0);
// everynth([1,2,3,4,5,6], 2) -> [ 1, 3, 5 ]
```
[⬆ 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.
@ -707,6 +722,22 @@ chainAsync([
[⬆ back to top](#table-of-contents)
### Compose functions
Use `Array.reduce()` to perform right-to-left function composition.
The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
```js
const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));
/*
const add5 = x => x + 5
const multiply = (x, y) => x * y
const multiplyAndAdd5 = compose(add5, multiply)
multiplyAndAdd5(5, 2) -> 15
*/
```
[⬆ back to top](#table-of-contents)
### Curry
Use recursion.
@ -725,9 +756,9 @@ const curry = (fn, arity = fn.length, ...args) =>
[⬆ back to top](#table-of-contents)
### Pipe
### Pipe functions
Use `Array.reduce()` to perform left-to-right function composition.
Use `Array.reduce()` with the spread operator (`...`) to perform left-to-right function composition.
The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
```js
@ -967,7 +998,29 @@ const speak = message => {
[⬆ back to top](#table-of-contents)
## Node
### Write a JSON to a file
### Read file as array of lines
Use `readFileSync` function in `fs` node package to create a `Buffer` from a file.
convert buffer to string using `toString(encoding)` function.
creating an array from contents of file by `split`ing file content line by line(each `\n`).
```js
const fs = require('fs');
const readFileToArray = filename => fs.readFileSync(filename).toString('UTF8').split('\n');
/*
contents of test.txt :
line1
line2
line3
___________________________
let arr = readFileToArray('test.txt')
console.log(arr) // -> ['line1', 'line2', 'line3']
*/
```
[⬆ back to top](#table-of-contents)
### Write JSON to file
Use `fs.writeFile()`, template literals and `JSON.stringify()` to write a `json` object to a `.json` file.
@ -980,6 +1033,30 @@ const jsonToFile = (obj, filename) => fs.writeFile(`${filename}.json`, JSON.stri
[⬆ back to top](#table-of-contents)
## Object
### Clean JSON object
Use `Object.keys()` method to loop over given json object and deleting keys that are not `include`d in given array.
also if you give it a special key(`childIndicator`) it will search deeply inside it to apply function to inner objects too.
```js
const cleanObj = (obj, keysToKeep = [], childIndicator) => {
Object.keys(obj).forEach(key => {
if (key === childIndicator) {
cleanObj(obj[key], keysToKeep, childIndicator);
} else if (!keysToKeep.includes(key)) {
delete obj[key];
}
})
}
/*
testObj = {a: 1, b: 2, children: {a: 1, b: 2}}
cleanObj(testObj, ["a"],"children")
console.log(testObj)// { a: 1, children : { a: 1}}
*/
```
[⬆ back to top](#table-of-contents)
### Object from key-value pairs
Use `Array.reduce()` to create and combine key-value pairs.
@ -1114,6 +1191,20 @@ const truncate = (str, num) =>
[⬆ back to top](#table-of-contents)
## Utility
### 3-digit hexcode to 6-digit hexcode
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.
```js
const convertHex = shortHex =>
shortHex[0] == '#' ? ('#' + shortHex.slice(1).split('').map(x => x+x).join('')) :
('#' + shortHex.split('').map(x => x+x).join(''));
// convertHex('#03f') -> '#0033ff'
// convertHex('05a') -> '#0055aa'
```
[⬆ back to top](#table-of-contents)
### Escape regular expression
Use `replace()` to escape special characters.
@ -1300,17 +1391,6 @@ const rgbToHex = (r, g, b) => ((r << 16) + (g << 8) + b).toString(16).padStart(6
[⬆ back to top](#table-of-contents)
### Swap values of two variables
Use array destructuring to swap values between two variables.
```js
[varA, varB] = [varB, varA];
// [x, y] = [y, x]
```
[⬆ back to top](#table-of-contents)
### URL parameters
Use `match()` with an appropriate regular expression to get all key-value pairs, `Array.reduce()` to map and combine them into a single object.

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@ -0,0 +1,11 @@
### 3-digit hexcode to 6-digit hexcode
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.
```js
const convertHex = shortHex =>
shortHex[0] == '#' ? ('#' + shortHex.slice(1).split('').map(x => x+x).join('')) :
('#' + shortHex.split('').map(x => x+x).join(''));
// convertHex('#03f') -> '#0033ff'
// convertHex('05a') -> '#0055aa'
```

6
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@ -1,8 +1,8 @@
### Array concatenation
Use `Array.concat()` to concatenate an array with any additional arrays and/or values, specified in `args`.
Use Array spread operators (`...`) to concatenate an array with any additional arrays and/or values, specified in `args`.
```js
const ArrayConcat = (arr, ...args) => [].concat(arr, ...args);
// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 2, 3, [4]]
const ArrayConcat = (arr, ...args) => [...arr,...args];
// ArrayConcat([1], [1, 2, 3, [4]]) -> [1, 1, 2, 3, [4]]
```

6
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@ -1,9 +1,9 @@
### Array without
Use `Array.filter()` to create an array excluding all given values.
Use `Array.filter()` to create an array excluding(using `!Array.includes()`) all given values.
```js
const without = (arr, ...args) => arr.filter(v => args.indexOf(v) === -1);
// without[2, 1, 2, 3], 1, 2) -> [3]
const without = (arr, ...args) => arr.filter(v => !args.includes(v));
// 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 ]
```

2
snippets/array-zip.md
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@ -6,7 +6,7 @@ If lengths of the argument-arrays vary, `undefined` is used where no value could
```js
const zip = (...arrays) => {
const maxLength = Math.max.apply(null, arrays.map(a => a.length));
const maxLength = Math.max(...arrays.map(x => x.length));
return Array.from({length: maxLength}).map((_, i) => {
return Array.from({length: arrays.length}, (_, k) => arrays[k][i]);
})

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@ -0,0 +1,21 @@
### Clean JSON object
Use `Object.keys()` method to loop over given json object and deleting keys that are not `include`d in given array.
also if you give it a special key(`childIndicator`) it will search deeply inside it to apply function to inner objects too.
```js
const cleanObj = (obj, keysToKeep = [], childIndicator) => {
Object.keys(obj).forEach(key => {
if (key === childIndicator) {
cleanObj(obj[key], keysToKeep, childIndicator);
} else if (!keysToKeep.includes(key)) {
delete obj[key];
}
})
}
/*
testObj = {a: 1, b: 2, children: {a: 1, b: 2}}
cleanObj(testObj, ["a"],"children")
console.log(testObj)// { a: 1, children : { a: 1}}
*/
```

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@ -0,0 +1,14 @@
### Compose functions
Use `Array.reduce()` to perform right-to-left function composition.
The last (rightmost) function can accept one or more arguments; the remaining functions must be unary.
```js
const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));
/*
const add5 = x => x + 5
const multiply = (x, y) => x * y
const multiplyAndAdd5 = compose(add5, multiply)
multiplyAndAdd5(5, 2) -> 15
*/
```

2
snippets/initialize-array-with-range.md
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@ -5,6 +5,6 @@ You can omit `start` to use a default value of `0`.
```js
const initializeArrayRange = (end, start = 0) =>
Array.apply(null, Array(end - start)).map((v, i) => i + start);
Array.from({ length: end - start }).map((v, i) => i + start);
// initializeArrayRange(5) -> [0,1,2,3,4]
```

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@ -1,10 +1,11 @@
### Convert JSON to date
### JSON to date
Converts dates coming from ajax as JSON to readable format `dd/mm/yyyy`
Use `Date()`, to convert dates in JSON format to readable format (`dd/mm/yyyy`).
```js
const jsonToDate = arr => {
const dt = new Date(parseInt(arr.toString().substr(6)));
return `${ dt.getDate() }/${ dt.getMonth() + 1 }/${ dt.getFullYear() }`};
const dt = new Date(parseInt(arr.toString().substr(6)));
return `${ dt.getDate() }/${ dt.getMonth() + 1 }/${ dt.getFullYear() }`
};
// jsonToDate(/Date(1489525200000)/) -> "14/3/2017"
```

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@ -1,6 +1,6 @@
### Pipe
### Pipe functions
Use `Array.reduce()` to perform left-to-right function composition.
Use `Array.reduce()` with the spread operator (`...`) to perform left-to-right function composition.
The first (leftmost) function can accept one or more arguments; the remaining functions must be unary.
```js

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@ -0,0 +1,19 @@
### Read file as array of lines
Use `readFileSync` function in `fs` node package to create a `Buffer` from a file.
convert buffer to string using `toString(encoding)` function.
creating an array from contents of file by `split`ing file content line by line(each `\n`).
```js
const fs = require('fs');
const readFileToArray = filename => fs.readFileSync(filename).toString('UTF8').split('\n');
/*
contents of test.txt :
line1
line2
line3
___________________________
let arr = readFileToArray('test.txt')
console.log(arr) // -> ['line1', 'line2', 'line3']
*/
```

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@ -1,8 +0,0 @@
### Swap values of two variables
Use array destructuring to swap values between two variables.
```js
[varA, varB] = [varB, varA];
// [x, y] = [y, x]
```

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@ -0,0 +1,8 @@
### Take every nth element
Use `Array.filter()` to create a new array that contains every nth element of a given array.
```js
const everynth = (arr, nth) => arr.filter((e, i) => i % nth === 0);
// everynth([1,2,3,4,5,6], 2) -> [ 1, 3, 5 ]
```

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@ -1,4 +1,4 @@
### Write a JSON to a file
### Write JSON to file
Use `fs.writeFile()`, template literals and `JSON.stringify()` to write a `json` object to a `.json` file.

10
tag_database
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@ -1,3 +1,4 @@
3-digit-hexcode-to-6-digit-hexcode:utility
anagrams-of-string-(with-duplicates):string
array-concatenation:array
array-difference:array
@ -15,8 +16,10 @@ capitalize-first-letter:string
chain-asynchronous-functions:function
check-for-palindrome:string
chunk-array:array
clean-JSON-object:object
collatz-algorithm:math
compact:array
compose-functions:function
count-occurrences-of-a-value-in-array:array
current-URL:browser
curry:function
@ -62,11 +65,12 @@ object-to-key-value-pairs:object
ordinal-suffix-of-number:utility
percentile:math
pick:array
pipe:function
pipe-functions:function
powerset:math
promisify:function
random-integer-in-range:utility
random-number-in-range:utility
read-file-as-array-of-lines:node
redirect-to-URL:browser
reverse-a-string:string
RGB-to-hexadecimal:utility
@ -81,8 +85,8 @@ sort-characters-in-string-(alphabetical):string
speech-synthesis-(experimental):media
standard-deviation:math
sum-of-array-of-numbers:array
swap-values-of-two-variables:utility
tail-of-list:array
take-every-nth-element:array
take-right:array
take:array
truncate-a-string:string
@ -92,4 +96,4 @@ UUID-generator:utility
validate-email:utility
validate-number:utility
value-or-default:utility
write-json-to-file:node
write-JSON-to-file:node