Javascript chain multiple function instead of passing function as argument

Question

I did a findMaxChar count algorithm practice, manage to get it to worked but my call method can be improved.

const myStr = 'Lorem Ipsummm'

function findRepeatable(myStr){
  let charMap = {}
  for(let char of myStr){
    if(charMap[char]) {
      charMap[char]++
    }else{
      charMap[char] = 1
    }
  }
  return charMap
}

function findMostRepeated(obj){
   let maxChar = '',
   max = 0
   for(let char in obj){
     if(obj[char] > max){
       max = obj[char]
       maxChar = char
     }
  }

  return `${maxChar}: ${max}`
}

console.log(findMostRepeated(findRepeatable(myStr)))

I'm passing function as argument, how can I make it to chain like this

findMostRepeated()
.findRepeatable()

https://jsbin.com/katixefoxe/edit?html,js,console

Your solution is better then chaining because chaining requires an object with state, while your solution is functional - each function knows how to do one thing without having side effects, and you can combine multiple functions to get a result. — Ori Drori
– Ori Drori, Commented Dec 23, 2017 at 11:18
^ Agreed, though if you do NEED to chain it, wrap it in a class and create instance of that class — Ayush Gupta
– Ayush Gupta, Commented Dec 23, 2017 at 11:21
@OriDrori passing function as argument is ok? I felt it's hard to read. — Madeline Ries
– Madeline Ries, Commented Dec 23, 2017 at 11:22
If you feel it is hard to read, then assign the first result to a variable, and pass that. That is perfectly fine. — trincot
– trincot, Commented Dec 23, 2017 at 11:24
@MadelineRies - functional programming takes some getting used to. However, when you do, it's very readable, because you can see the input, and the flow. — Ori Drori
– Ori Drori, Commented Dec 23, 2017 at 11:34

Dan Prince · Accepted Answer · 2017-12-23 12:10:59Z

1

Many functional libraries come with a pipe function that can be used for "chaining".

pipe(findRepeatable, findMostRepeated)(myStr)

It's easy to implement yourself.

function pipe(...funcs) {
  return function(value) {
    for (func of funcs) {
      value = value(func)
    }

    return value;
  }
}

edited Dec 23, 2017 at 12:10

answered Dec 23, 2017 at 11:45

Dan Prince

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1 Comment

Nina Scholz Over a year ago

or just a single line const pipe = (...funcs) => value => funcs.reduce((v, f) => f(v), value);

Jonas Wilms · Accepted Answer · 2017-12-23 11:36:31Z

0

 class CharMap extends Map {
  constructor(str){
    super();
    for(var char of str)
      this.add(char);
  }
  add(char){
    this.set(char, (this.get(char) || 0) + 1);
  }
  max(){
    return this.sortDesc()[0];
  }
  sortDesc(){
    return [...this].sort(([char, a], [char2, b]) => b - a);
  }
 }

So you can do:

 const map = new CharMap("abbccddeee");
 console.log(map.max());

To get the char and its count:

 const [char, count] = map.max();

edited Dec 23, 2017 at 11:36

answered Dec 23, 2017 at 11:26

Jonas Wilms

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1 Comment

Madeline Ries Over a year ago

this is way too advance haha!

somanalytics · Accepted Answer · 2017-12-23 11:41:08Z

0

try:

const myStr = 'Lorem Ipsummm'
var myObj ={
  charMap:{},
findRepeatable:function (myStr){

  for(let char of myStr){
if(this.charMap[char]) {
  this.charMap[char]++
}else{
  this.charMap[char] = 1
}
  }
  return this;
},
findMostRepeated: function (obj){
   let maxChar = '',
   max = 0
   for(let char in this.charMap){
     if(this.charMap[char] > max){
       max = this.charMap[char]
       maxChar = char
     }
  }

  return `${maxChar}: ${max}`;
}
}

console.log(myObj.findRepeatable(myStr).findMostRepeated())

answered Dec 23, 2017 at 11:41

somanalytics

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