diff --git a/src/index.js b/src/index.js
index 9258781..3755ebf 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,249 +1,282 @@
-var responseCount, currentQuestion, options,
-questions, responses, quizData, question, j,
-$question, $resetButton, isQuestionAnswered
+let options = {url: `data/quiz.json? ${Date.now()}`}
 
-responseCount = 0
-currentQuestion = 0
-options = {
-  url: 'data/quiz.json?' + Date.now()
+function loadResponses() {
+  let quizData
+  try {
+    quizData = JSON.parse(localStorage.getItem('quiz')) || {responses: [], responseCount: 0, currentQuestion: 0}
+  } catch (e) {}
+  return quizData
 }
 
-$.ajax({
-  url: options.url
-}).done(function(data) {
-  questions = data.questions
+function saveResponses(responses, responseCount, currentQuestion) {
+  let quizData = {responses, responseCount, currentQuestion}
+  localStorage.setItem('quiz', JSON.stringify(quizData))
+}
 
-  // Load data from past reponses
-  try {
-    quizData = JSON.parse(localStorage.getItem('quiz'))
-    responses = quizData.responses || []
-    currentQuestion = quizData.currentQuestion || -1
-    responseCount = quizData.responseCount || -1
-  } catch (e) {}
+function appendProgressBar() {
+  $('body')
+    .append(`<div style="position: fixed; bottom: 0; background: #eee; width: 100%; height: 6px; ">
+      <div id="progress" style="background: #1678c2; width: 1%;">&nbsp;</div>
+      </div>`)
+}
 
-  if (quizData == null) {
-    quizData = {
-      responses: []
-    }
-    responses = quizData.responses
+function appendTitle(title) {
+  $('#quiz')
+    .append(`<h1 class="ui header"> ${title} </h1>
+             <form id="quiz-form" class="ui form"></form>`)
+}
+
+function buildInput(i, type, options, responses) {
+  let input 
+  switch (type) {  
+
+    // Multiple options
+    case 'checkbox':
+    case 'radio':
+      input = '<div class="inline fields">'
+      options.forEach((option, j) => {
+        let checked = responses[i] && responses[i].indexOf(option.label) !== -1 ? 'checked' : ''
+
+        input += `<div class="field">
+          <div class="ui checkbox ${type}">
+          <input type="${type}" ${checked} name="question_${i}" id="question_${i}_${j}" value="${option.label}">
+          <label for="question_${i}_${j}">${option.label}</label>
+          </div>
+          </div>`
+      })
+      input += '</div>'
+      break
+
+    // Set of inputs (composed response)
+    case 'inputs':
+      input = '<table>'
+      options.forEach((option, j) => {
+        let value = responses[i] ? responses[i][j] : ''
+        
+        input += `<tr>
+          <td><label for="question_${i}_${j}">${option.label}</label></td>
+          <td width="15px"></td>
+          <td><div class="ui input">
+          <input type="text" placeholder="Response..." name="question_${i}" id="question_${i}_${j}" value="${value}" />
+          </div></td>
+          </tr>
+          <tr><td colspan="3">&nbsp;</tr></tr>`
+      })
+      input += '</table>'
+      break
+
+    // Default: simple input
+    default:
+      let value = responses[i] ? responses[i] : ''
+      
+      input = `<div class="ui input fluid">
+        <input type="text" placeholder="Response..." name="question_${i}" value="${value}" />
+        </div>`
   }
+  return input
+}
 
+function appendQuestion(i, question, input) {
+  const $question = $(`<div id="question-${i}" class="ui card" style="width: 100%;">
+      <div class="content">
+      <div class="header">${question.problem}</div>
+      </div>
+      <div class="content">
+      ${input}
+      </div>
+      </div>`
+    ).css('display', 'none')
 
-  // Append the progress bar to DOM
-  $('body')
-    .append('<div style="position: fixed; bottom: 0; background: #eee; width: 100%; height: 6px; ">' +
-      '<div id="progress" style="background: #1678c2; width: 1%;">&nbsp;</div>' +
-      '</div>')
+  $('#quiz-form')
+    .append($question)
+}
 
-  // Append title and form to quiz
-  $('#quiz')
-    .append('<h1 class="ui header">' + data.title + '</h1>')
-    .append('<form id="quiz-form" class="ui form"></form>')
+function showCurrentQuestion(currentQuestion) {
+  $('#quiz-form')
+      .find(`#question-${currentQuestion}`)
+      .css('display', 'block')
+}
 
-  // For each question of the json,
-  for (var i = 0; i < data.questions.length; i++) {
-    question = data.questions[i]
+function updateProgressBar(responseCount, questions) {
+  $('#progress')
+      .css('width', (responseCount / questions.length * 100) + '%')
+}
 
-    if (question.input === undefined) {
-      question.input = {
-        type: 'input'
+function checkAllQuestionsAnswered(responseCount, questions) {
+  if (responseCount === questions.length) {
+    $('#submit-response').css('display', 'none')
+    $('#quiz').append('<div>Thank you for your responses.<br /><br /> </div>')
+    $('#quiz').append('<button class="ui primary button" onclick="window.print()" >Print responses</button>')
+  }
+}
+
+function addResetButton() {
+  const $resetButton = $('<button class="ui button negative">Reset</button>')
+  $resetButton.on('click', function() {
+    localStorage.removeItem('quiz')
+    location.reload();
+  })
+  $('#quiz').append($resetButton)
+}
+
+function putResponsesIntoArray(question, $inputs, responses, currentQuestion) {
+  let result = responses.map(item => item)
+
+  switch (question.input.type) {
+    case 'checkbox':
+    case 'radio':
+      result[currentQuestion] = []
+      $(`[name=${$inputs.attr('name')}]:checked`).each((i, input) =>{
+        result[currentQuestion].push(input.value)
+      })
+      if (result[currentQuestion].length === 0) {
+        result[currentQuestion] = null
       }
-    }
+      break
+    case 'inputs':
+      result[currentQuestion] = []
+      $inputs.each((i, input) => {
+        result[currentQuestion].push(input.value)
+      })
+      break
+    default:
+      result[currentQuestion] = $inputs.val()
+  }
+  return result
+}
 
-    // Construct the input depending on question type
+function getResponseCount(responses, questions) {
+  let responseCount = 0
+  responses.forEach((response, i) => {
+    let question = questions[i]
     switch (question.input.type) {
-
-      // Multiple options
       case 'checkbox':
       case 'radio':
-        var input = '<div class="inline fields">'
-        for (j = 0; j < question.input.options.length; j++) {
-          var option = question.input.options[j]
-          var type = question.input.type
-
-          if (!!responses[i] && responses[i].indexOf(option.label) !== -1) {
-            var checked = 'checked'
-          } else {
-            var checked = ''
-          }
-
-          input += '<div class="field">' +
-            '<div class="ui checkbox ' + type + '">' +
-            '<input type="' + type + '" ' + checked + ' name="question_' + i + '" id="question_' + i + '_' + j + '" value="' + option.label + '">' +
-            '<label for="question_' + i + '_' + j + '">' + option.label + '</label>' +
-            '</div>' +
-            '</div>'
-        }
-        input += '</div>'
-        break
-
-        // Set of inputs (composed response)
       case 'inputs':
-        var input = '<table>'
-        for (j = 0; j < question.input.options.length; j++) {
-          var option = question.input.options[j]
-          var type = 'checkbox'
-
-          if (!!responses[i]) {
-            var value = responses[i][j]
-          } else {
-            var value = ''
-          }
-
-          input += '<tr>' +
-            '<td><label for="question_' + i + '_' + j + '">' + option.label + '</label></td>' +
-            '<td width="15px"></td>' +
-            '<td><div class="ui input">' +
-            '<input type="text" placeholder="Response..." name="question_' + i + '" id="question_' + i + '_' + j + '" value="' + value + '" />' +
-            '</div></td>' +
-            '</tr>' +
-            '<tr><td colspan="3">&nbsp;</tr></tr>'
+        if (response && response.join('')) {
+          responseCount++
         }
-        input += '</table>'
         break
-
-        // Default: simple input
       default:
-        if (!!responses[i]) {
-          var value = responses[i]
-        } else {
-          var value = ''
+        if (response) {
+          responseCount++
         }
-        var input = '<div class="ui input fluid">' +
-          '<input type="text" placeholder="Response..." name="question_' + i + '" value="' + value + '" />' +
-          '</div>'
     }
+  })
+  return responseCount
+}
 
-    $question = $('<div id="question-' + i + '" class="ui card" style="width: 100%;">' +
-      '<div class="content">' +
-      '<div class="header">' + question.problem + '</div>' +
-      '</div>' +
-      '<div class="content">' +
-      input +
-      '</div>' +
-      '</div>'
-    ).css('display', 'none')
+function isArray(obj) {
+  return Object.prototype.toString.call(obj) === '[object Array]'
+}
+
+function checkIfQuestionAnswered(responses, currentQuestion) {
+  let isQuestionAnswered = !responses[currentQuestion] ? false : true
+    
+  if (responses[currentQuestion] && responses[currentQuestion].length && isArray(responses[currentQuestion])) {
+    responses[currentQuestion].forEach((response) => {
+      if (!response) {
+        isQuestionAnswered = false
+      }
+    })
+  }
+  return isQuestionAnswered
+}
 
-    $('#quiz-form')
-      .append($question)
+function displayNextQuestion(currentQuestion) {
+  let result = currentQuestion
+  $('#quiz-form')
+        .find(`#question-${result}`).css('display', 'none')
+        result++
+
+      $('#quiz-form')
+        .find(`#question-${result}`).css('display', 'block')
+  return result
+}
+
+function checkForFinalMessage(responseCount, questions) {
+  if (responseCount === questions.length) {
+    $('#submit-response').css('display', 'none')
+    $('#quiz').append(`<div>Thank you for your responses.<br /><br /> </div>
+                       <button class="ui primary button" onclick="window.print()" >Print responses</button>`)
+  }
+}
+
+$.ajax({
+  url: options.url
+}).done((data) => {
+  const { questions , title} = data;
+
+  // Load data from past reponses
+  let quizData = loadResponses()
+  let {currentQuestion=0, responseCount=0, responses=[]} = quizData
+  
+  // Append the progress bar to DOM
+  appendProgressBar()
+  
+  // Append title and form to quiz
+  appendTitle(title)
+  
+  // For each question of the json,
+  questions.forEach((question, i) => {
+    const {input: {type= 'input', options=[]} = {}, problem} = question
+          
+    if (question.input === undefined) {
+      question.input = {
+        type: 'input'
+      }
+    }
+
+    // Construct the input depending on question type
+    let input = buildInput(i, type, options, responses)   
+    appendQuestion(i, question, input)
 
     // Show current question
-    $('#quiz-form')
-      .find('#question-' + currentQuestion)
-      .css('display', 'block')
+    showCurrentQuestion(currentQuestion)
 
     // Update progress bar
-    $('#progress')
-      .css('width', (responseCount / questions.length * 100) + '%')
-  }
+    updateProgressBar(responseCount, questions)
+  })
 
   // Add button to submit response
   $('#quiz')
     .append('<button id="submit-response" class="ui primary button">Submit response</button>')
 
   // Is case all questions have been responded
-  if (responseCount === questions.length) {
-    $('#submit-response').css('display', 'none')
-    $('#quiz').append('<div>Thank you for your responses.<br /><br /> </div>')
-    $('#quiz').append('<button class="ui primary button" onclick="window.print()" >Print responses</button>')
-  }
+  checkAllQuestionsAnswered(responseCount, questions)
 
   // Add a reset button that will redirect to quiz start
-  $resetButton = $('<button class="ui button negative">Reset</button>')
-  $resetButton.on('click', function() {
-    localStorage.removeItem('quiz')
-    location.reload();
-  })
-  $('#quiz').append($resetButton)
+  addResetButton()
 
   // Actions on every response submission
-  $('#submit-response').on('click', function() {
-    var $inputs = $('[name^=question_' + currentQuestion + ']')
-    var question = questions[currentQuestion]
+  $('#submit-response').on('click', () => {
+    
+    const $inputs = $(`[name^=question_${currentQuestion}]`)
+    let question = questions[currentQuestion]
 
     // Behavior for each question type to add response to array of responses
-    switch (question.input.type) {
-      case 'checkbox':
-      case 'radio':
-        responses[currentQuestion] = []
-        $('[name=' + $inputs.attr('name') + ']:checked').each(function(i, input) {
-          responses[currentQuestion].push(input.value)
-        })
-        if (responses[currentQuestion].length === 0) {
-          responses[currentQuestion] = null
-        }
-        break
-      case 'inputs':
-        responses[currentQuestion] = []
-        $inputs.each(function(i, input) {
-          responses[currentQuestion].push(input.value)
-        })
-        break
-      default:
-        responses[currentQuestion] = $inputs.val()
-    }
+    responses = putResponsesIntoArray(question, $inputs, responses, currentQuestion)
 
     // Set the current responses counter
-    var responseCount = 0
-    for (i = 0; i < responses.length; i++) {
-      question = questions[i]
-      switch (question.input.type) {
-        case 'checkbox':
-        case 'radio':
-        case 'inputs':
-          if (!!responses[i] && !!responses[i].join('')) {
-            responseCount++
-          }
-          break
-        default:
-          if (!!responses[i]) {
-            responseCount++
-          }
-      }
-    }
+    let responseCount = getResponseCount(responses, questions)
 
     // Update progress bar
-    $('#progress')
-      .css('width', (responseCount / questions.length * 100) + '%')
+    updateProgressBar(responseCount, questions)
 
     // Check if question had a valid answer
-    isQuestionAnswered = true
-    if (!responses[currentQuestion]) {
-      isQuestionAnswered = false
-    }
-    if (!!responses[currentQuestion] && !!responses[currentQuestion].length) {
-      for (j = 0; j < responses[currentQuestion].length; j++) {
-        if (!responses[currentQuestion][j]) {
-          isQuestionAnswered = false
-        }
-      }
-    }
-
-    if (!isQuestionAnswered) {
+    if (!checkIfQuestionAnswered(responses, currentQuestion)) {
       // Alert user of missing response
       alert('You must give a response')
     } else {
 
       // Display next question
-      $('#quiz-form')
-        .find('#question-' + currentQuestion).css('display', 'none')
-      currentQuestion = currentQuestion + 1
-
-      $('#quiz-form')
-        .find('#question-' + currentQuestion).css('display', 'block')
-
+      currentQuestion = displayNextQuestion(currentQuestion)
+      
       // If it was the las question, display final message
-      if (responseCount === questions.length) {
-        $('#submit-response').css('display', 'none')
-        $('#quiz').append('<div>Thank you for your responses.<br /><br /> </div>')
-        $('#quiz').append('<button class="ui primary button" onclick="window.print()" >Print responses</button>')
-      }
+      checkForFinalMessage(responseCount, questions)
     }
 
     // Save current state of the quiz
-    quizData.responses = responses
-    quizData.responseCount = responseCount
-    quizData.currentQuestion = currentQuestion
-    localStorage.setItem('quiz', JSON.stringify(quizData))
+    saveResponses(responses, responseCount, currentQuestion)
   })
-})
+})
\ No newline at end of file