https://github.com/victorvoid/reduces-js
:honeybee: reduce everywhere
https://github.com/victorvoid/reduces-js
Last synced: 10 months ago
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:honeybee: reduce everywhere
- Host: GitHub
- URL: https://github.com/victorvoid/reduces-js
- Owner: victorvoid
- Created: 2016-08-06T00:11:57.000Z (almost 10 years ago)
- Default Branch: master
- Last Pushed: 2016-08-17T03:17:04.000Z (almost 10 years ago)
- Last Synced: 2025-02-26T16:19:38.793Z (over 1 year ago)
- Language: JavaScript
- Homepage:
- Size: 11.7 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# Reduces Js
Understand Javascript Array Reduce with examples everywhere.
# When to use Reduce ?
You may use reduce when to want to find a cumulative or concatenated value based on elements across the array,
and a cumulative value can to be one way to solve many problems.
## Examples
1.
```js
/*It should remove all values from list a, which are present in list b.
difference([1,2],[1]) == [2] difference([1,2,2,2,3],[2]) == [1,3] */
let array_diff = (a, b) => a.reduce((prev, curr) => (!b.includes(curr) && prev.push(curr), prev), [])
```
2.
```js
/* Returns the sum of all the multiples of 3 or 5 below the number passed in.
10 => 23, 5 => 3*/
let multiplebelow = number =>
number <= 0 ? 0 :
Array.from(new Array(number-1), (x, i) => i + 1)
.reduce((prev, curr) => (curr % 3 == 0 || curr % 5 == 0) ? prev + curr: prev ,0)
```
3.
```js
/*An isogram is a word that has no repeating letters, consecutive or non-consecutive.
aspol => true, asspol => false*/
let isIsogram = str =>
!str
.toLowerCase()
.split('')
.reduce((prev, curr, i, array) => array
.slice(array.indexOf(curr)+1)
.includes(curr) ? prev + 1: prev + 0, 0) > 0
```
4.
```js
// ('1234fnb') => '###4fnb'
let maskify = cc =>
cc
.split('')
.reduce((total, curr, currentIndex, arr) =>
currentIndex < (arr.length-4) ? total + '#': total + arr[currentIndex], '')
```
5.
```js
//promise all
const fs = require('fs');
function promiseAll (arr) {
return Promise.all(arr)
.then(function success(res){
return res.map(a => JSON.parse(a))
.reduce((init,actual) => {
init = init.concat(actual)
return init;
},[]);
})
.catch(function error(err) {
throw err;
});
}
function readFile (path) {
return new Promise(function(resolve, reject) {
fs.readFile(path,'utf8',function(err, res) {
err ? reject(err) : resolve(res);
});
});
}
promiseAll([
readFile('./file01.json'),
readFile('./file02.json')
])
.then( res => console.log(res))
.catch(err => console.error(err));
```
6.
```js
let users_values = {
name: [
"Victor Igor"
, "José Carlos"
, "Joao Messias"
, "Andy Self"
, "Archer Gly"
],
username: [
"vitus"
, "jose123"
, "juau"
, "joaome"
, "andy321"
]
};
let addUsers = user => user['name']
.reduce((prev, curr, i, a) => {
prev.push({
name: curr
, bio: "place your bio here"
, dateregister: Date.now()
, avatarpath: "place your avatar here"
, auth: {
username: user['username'][i]
, email: user['username'][i]+"@hotmail.com"
, password: curr + Math.random().toString(36)
, online: true
, disabled: false
, hashtoken: 'hash()'
}
})
return prev;
},[]);
```
7.
```js
//alphabet position
const fs = require('fs');
let alphabet = fs.readFileSync('alphabet.txt', 'utf8')
.trim()
.split(' ')
.map(n => n.toLowerCase())
let alphabetPosition = (text) => {
return text
.split('')
.filter(n => n != ' ')
.reduce((prev, curr) => prev.concat(alphabet.indexOf(curr) + 1), [])
.join(' ')
}
```
8.
```js
/*
deleteNth ([1,1,1,1],2) // return [1,1]
deleteNth ([20,37,20,21],1) // return [20,37,21]
<=
deleteNth([16,16,16,20,20,1,2], 2) //return [16,16,20,20,1,2]
*/
function deleteNth(arr,x){
'use strict'
let countArr = (v, newarr) => {
let obj = newarr.reduce((p, v)=>{
if(v in p)
p[v]++;
else
p[v] = 1;
return p;
}, {})
return obj[v];
};
}
```