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//Currying is when you break down a function that takes multiple arguments into a //series of functions that take part of the arguments.
//converts a function f of two arguments into a function of one argument that partially applies f.
  def curry[A,B,C](f: (A,B) => C): A => (B => C) =
  		(a: A) => (b: B) => f(a,b)  
  //> curry: [A, B, C](f: (A, B) => C)A => (B => C)

xiaoyunyang

import express from  'express'
import path from 'path'
import fs from 'fs'

const app = express()
app.set("port", process.env.PORT || 3001)

// Middleware that serves static file ======================================

app.use('/static', (req, res, next) => {

xiaoyunyang

var multThenAdd = num => {
   return mul => add => {
      return num * mul + add
   }
}

var timesTwoPlusFour = (num) => multThenAdd(num)(2)(4)

timesTwoPlusFour(1) //> 6
timesTwoPlusFour(10) //> 24

xiaoyunyang

var myFun2 = function() { 
  var num = -1
  function incrementUntil(max) { 
     if(num >= max) return num 
     num++
     incrementUntil(max)
   }
   incrementUntil(3)
   return num 
}	

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var incrementUntil = function(max) {
   var inc = function(num) { 
      if(num >= max) return num 
      return inc(num+1)
    }
    return (num) => inc(num)
}
	
incrementUntil(4)(1) //> 4
incrementUntil(8)(3) //> 8

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const getInfoFromURL = path => {
   const URL = require(“url”).URL;
   const myUrl = new URL(path)
   const pathname = myUrl.pathname
   
   const getUsernameFromURL = pathname => {
      const regex = new RegExp(‘/@’);
      const username = pathname.split(regex).slice(1)[0]
      if(!username) {
        return “Error in parsing: URL needs to be in format://hostname:port/@username”

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num = 0
var myFun2 = function() { 
   var num = -1
   incrementUntil(3)
  return num 
}

myFun2() //> -1 ……Why?
num //> 3

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num = 0
var myFun = function() { 
   incrementUntil(3)
    return num 
}

myFun() //> 3
num //> 3

xiaoyunyang

// BAD
function valIncrementer(val, disabled) {
    var nextVal = val + 1

    function firstStageSetter1() {
        if(val >= 10) {
            nextVal = 10 //clip it to high limit value
            secondStageSetter()
        }
    }

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let vals = Array.from({length: 13}, (v,i) => i)
//> (13) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

vals = vals.map(v => v-1)
//> (13) [-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

let res = vals.map(v => (
  {val: v, notDisabled: valIncrementer(v, false), disabled: valIncrementer(v, true) }
))