letterFrequency.js

/*

Given a page of text, output the characters ordered from highest to lowest occurrence.

for example, the output for 'banana!' is
a: 3
n: 2
b: 1
!: 1

*/

var pageoftext = 'banana!'

function findFrequency (text) {
  var letters = {} // { a: 2, b: 10 }
  // iterate through each letter
    for (var i = 0; i < text.length; i++) {
      var character = text.charAt(i)
      if (character !== ' ') {
        // make sure it is not a space
        if (letters[character]) {
          letters[character] += 1
          // add letter to object if it doesn't already exist
          // if letter exists, add to the count
        } else {
          letters[character] = 1
        }
      }
    }
  var arr = []
  for (var key in letters) {
    arr.push([key, letters[key]])
  }
  // [ ['b', 1], ['a', 2], ['!', 1] ]
  // sort the properties of object according to values
  arr.sort(function(a, b) {
    return b[1] - a[1] // reverse order, highest to lowest
    // if < 0, sort a to a lower index than b
    // if > 0, sort b to a lower index than a
    // if 0 leave it
  })

  return arr
}

console.log(findFrequency(pageoftext))