alex-cory

/**
 *    @example
 *    const list = ['a', 'b', 'c', 'c', 'c']
 *    const numOfCs = count(list, letter => letter === 'c')
 *    console.log(numOfCs) // 3
 */
const count = (ls, cb) => ls.reduce((count, item) => cb(item) ? ++count : count, 0)

alex-cory

const strip = toRemove => ({
  from: str => {
    const pattern = `(${toRemove.split('').join(')(')})`
    return str.replace(RegExp(pattern, 'ig'), c => '')
  }
})

strip('cool').from('coolio') // io

alex-cory

import { observer as observe, inject } from 'mobx'
import { withRouter } from 'react-router'
import React, { Component } from 'react'

// I wonder if this works
const observer = stores => Component => withRouter(inject(...stores)(observe(Component)))

@observer('store')
class MyComponent extends Component {
  // ...

alex-cory

// does not include special chars
const isUnique = str => !/([a-z0-9]).*?\1/i.test(str)

// includes special chars
const isUnique = str => !/^.*(.).*\1.*$/i.test(str)

alex-cory

var uniq = ar => Array.from(new Set(a))
var uniq = ar => [...new Set(a)]

// Others: https://stackoverflow.com/a/9229821/2782583

alex-cory

const isAllUp = s => s.match(/[^a-z]*/)[0].length === s.length
const isAllLow = s => s.match(/[a-z]*/)[0].length === s.length
const isCapitalized = s => s.substring(1, s.length).match(/[a-z]*/)[0].length === s.length - 1 && /^[A-Z]/.test(s)

console.log('All UP? expect: true got -> ', isAllUp('SOMEWORD'))
console.log('All UP? expect: false got -> ', isAllUp('Someword'))
console.log('All UP? expect: false got -> ', isAllUp('someword'))
console.log('All LOW? expect: true got -> ', isAllLow('someword'))
console.log('All LOW? expect: false got -> ', isAllLow('Someword'))
console.log('All LOW? expect: false got -> ', isAllLow('SOMEWORD'))

alex-cory

/**
 * by definition, primes cannot be negative
 */
const isPrime = value => {
    for(var i = 2; i < value; i++) {
        if(value % i === 0) {
            return false;
        }
    }
    return value > 1;

alex-cory

var closest = (nums, goal) => nums.reduce((prv, cur) => (
	Math.abs(prv - goal) > Math.abs(cur - goal) ? cur : prv
))
closest([-1, 2, 1, -4], 3) // should return 2

alex-cory

// Option 1: [0, ...., N]
var array = length => Array.from({ length }, (_, i) => i)

// Option 2: [0, ...., N]
var array = to => Array.from(Array(to), (_, i) => i)

// Option 3: [1, ....., N]
var array = length => Array.from({ length }, (_, i) => i + 1)

alex-cory

String.fromCharCode(...Array(123).keys()).slice(97).split('')