first_non_repeating_character.js

// Write a function named first_non_repeating_letter that takes a string input, 
// and returns the first character that is not repeated anywhere in the string.

// For example, if given the input 'stress', the function should return 't', 
// since the letter t only occurs once in the string, and occurs first in the string.

// As an added challenge, upper- and lowercase letters are considered the same character,
// but the function should return the correct case for the initial letter. For example, the input 'sTreSS' should return 'T'.

// If a string contains all repeating characters, it should return an empty string ("") 
// or None -- see sample tests.

// -------------------- My Solution -----------------------------------

function firstNonRepeatingLetter(s) {
    let stringArray = s.split("")
    let charObject = {}
    
    for (let char of stringArray) {
      if (char.toUpperCase() == char.toLowerCase()) {
          charObject[char.toLowerCase()] == undefined? charObject[char.toLowerCase()] = 1 : charObject[char.toLowerCase()] += 1 
      }
      else {
        charObject[char.toLowerCase()] == undefined? charObject[char.toLowerCase()] = 1 : charObject[char.toLowerCase()] += 1
      charObject[char.toUpperCase()] == undefined? charObject[char.toUpperCase()] = 1 : charObject[char.toUpperCase()] += 1
    
      }
    }
    
    for (let char of stringArray) {
      if (charObject[char] == 1) {
        return char
      } 
    }
    
    return ''
    
  }