pr2.js

/**
  determine character frequency of provided input: ex, "chicago"
  print the frequency as follows
  
  c: **
  h: *
  i: *
  a: *
  g: *
  o: *

  *     
  ******
  chiago
  
*/

const input = "chicago";
const values = {};  // use as a Set

// build data set
let maxFrequency = 0;
const keys = input.split('').filter((ch) => {
  const contains = ch in values;
  if (!contains) {
    values[ch] = 1;
  } else {
    values[ch] += 1;
  }

  if (values[ch] > maxFrequency) {
    maxFrequency = values[ch];
  }

  return !contains;
});

function printRow(key, value) {
  return `${key}: ` + Array.from({length: value}).map((x, i) => '*').join('') + "\n";
}

// vertical output
let result1 = keys.reduce((row, k, i) => (
  row + printRow(k, values[k])
), '');

// horizontal output: stars
let result2 = '';
for (let i = maxFrequency; i > 0; i--) {
  result2 += keys.reduce((line, k, n) => (
    line + ((values[k] >= i) ? '*' : " ")
  ), '') + "\n"
}
// horizontal output: chars
result2 += keys.reduce((row, k, i) => row + k)

console.log(result1);
console.log(result2);