Set values to dinamically created object using a loop

Question

I created an array from letters of a large string. Now I want to create an object which says how many times that letter is repeated in the array, but I can`t find a solution, please help me out a little.

This is what I done so far:

var str = "Lorem, ipsum dolor sit amet consectetur adipisicing elit. Illo commodi sint fuga autem nobis atque possimus";
var arr = str.split("");

arr.forEach(function(e, i) {
  if (e === " ") {
    //var index = arr.indexOf(e);
    arr.splice(i, 1);
  }
});

var obj = {};
var counter = 0;

arr.forEach(function(e, i) {
  obj[e] = 1;
});

arr2 = Object.keys(obj);
var counter = 0;

for (let c = 0; c < arr.length; c++) {
  for (let b = 0; b < arr2.length; b++) {
    if (arr2[b] == arr[c]) { // to find coincidences
      count++;
      // I'm lost here ..
    }
  }
}

Your first forEach loop won't work correctly. Use arr.filter instead. — Barmar
– Barmar, Commented Mar 6, 2019 at 23:33

Barmar · Accepted Answer · 2019-03-07 00:48:14Z

3

You need to increment the counter for each letter, not just set it to 1.

There's no need for the for loop at the end, or the counter variable. obj contains the counts that you want.

var str =
  "Lorem, ipsum dolor sit amet consectetur adipisicing elit. Illo commodi sint fuga autem nobis atque possimus";

var arr = str.split("");

arr = arr.filter(e => e != " ");

var obj = {};

arr.forEach(function(e) {
  if (e in obj) {
    obj[e]++;
  } else {
    obj[e] = 1;
  }
  // Could also be obj[e] = (obj[e] || 0) + 1
});

console.log(obj);

edited Mar 7, 2019 at 0:48

answered Mar 6, 2019 at 23:38

Barmar

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3 Comments

Roko C. Buljan Over a year ago

instead of looping twice (filter and than forEach) just to remove whitespaces, a simple delete obj[' '] would do the job

Barmar Over a year ago

Yeah, or just if (e != " ") in the second loop. Lots of ways to skin the cat.

Roko C. Buljan Over a year ago

Also, I know e represents a single character - not present in an Object prototype, but it's too easy for a beginner to remember this tricky in operator and get used to it, and one day stumble upon "valueOf" in {} === true. It's longer but definitely good to know Object.prototype.hasOwnProperty.call(obj, "prop")

Sergey Mell · Accepted Answer · 2019-03-07 00:12:44Z

0

As a fan of regex I'd propose a more short solution:

const str = 'Lorem, ipsum dolor sit amet consectetur adipisicing elit. Illo commodi sint fuga autem nobis atque possimus';

const result = {};

Array.prototype.forEach.call(str.replace(/[^\w]/g, ''), letter => {
    if (letter in result) return;
    result[letter] = str.match(new RegExp(letter, 'g')).length;
});

console.log(result);

You can change regex i flag in order to turn on/off case sensitivity.

edited Mar 7, 2019 at 0:12

answered Mar 6, 2019 at 23:48

Sergey Mell

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2 Comments

Roko C. Buljan Over a year ago

You can use \W instead of [^\w]... but why use W at all, it's the same as [^a-zA-Z0-9_] which in this multilingual UTF-8 world is something you should avoid even suggesting, unless you're not regexing phrases but some strict properties or data names.

Sergey Mell Over a year ago

Thank you for the recommendation, I appreciate

Roko C. Buljan · Accepted Answer · 2019-03-07 00:46:17Z

0

Using Array.from() ^_MDN and Array.prototype.reduce ^_MDN :

const str = "Lorem, ipsum dolor sit amet consectetur adipisicing elit. Illo commodi sint fuga autem nobis atque possimus";

const obj = Array.from(str).reduce((ob, c) => {
  ob[c] = ++ob[c] || 1;
  return ob;
}, {});

delete obj[' ']; // If needed remove data for whitespaces
console.log( obj )

Array.from(String) will convert a String to Array.
No need to remove whitespaces, you can do that later using Object delete
reduce will iterate over the array "reducing" it to an Object {}
The inner logic ob[c] = ++ob[c] || 1; just instantiates the property with the value 1, otherwise it increments it.

edited Mar 7, 2019 at 0:46

answered Mar 6, 2019 at 23:59

Roko C. Buljan

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