Javascript to-do application for native Javascript

Question

I did a simple to-do application for native Javascript. This is my first time, previously I used only jQuery. What recommendations would be useful?

https://codepen.io/denibudeyko/pen/MWyEmox

(function(window) {
  'use strict';

  // Initial Const 
  const input = document.getElementsByClassName('new-todo')[0]
  const todoList = document.getElementsByClassName('todo-list')[0]
  const items = document.querySelectorAll('.todo-list li')
  const clear = document.querySelector('.clear-completed')
  const todoCount = document.querySelector('.todo-count strong')

  // Add new task
  input.addEventListener('keyup', function(e) {

    var string = input.value;

    if (e.key == 'Enter') {
      const li = document.createElement('li')
      li.innerHTML = `
                    <div class="view">
                        <input class="toggle" type="checkbox" />
                        <label>${string}</label>
                        <button class="destroy"></button>
                    </div>
                    <input class="edit" value="${string}">
                `;

      todoList.appendChild(li);
      const childrenItem = li.querySelector('input.toggle')

      childrenItem.addEventListener('click', event => {
        toggleTaskStatusEvent(event.target)
      })

      input.value = '';
      updateCount();
    }
  })

  function updateCount() {
    todoCount.textContent = document.querySelectorAll('.todo-list li:not(.completed)').length;
  }

  updateCount()


  // Toggle Status
  document.querySelectorAll('.todo-list li').forEach(item => {

    const toggleCheckbox = item.querySelector('input.toggle')
    toggleCheckbox.addEventListener('click', event => {
      toggleTaskStatusEvent(event.target)
    })
  })

  // ToggleTaskStatus
  function toggleTaskStatusEvent(e) {
    const liParent = e.closest('li')
    liParent.classList.toggle('completed')
    updateCount()
  }

  clear.addEventListener('click', function() {
    document.querySelectorAll('.todo-list li.completed').forEach(item => {
      item.remove()
    })
  })

  // FiltersButtons
  document.querySelectorAll('ul.filters li').forEach(item => {
    const filterButton = item.children[0];
    filterButton.addEventListener('click', event => {
      runFilter(event.target)
    })
  })

  // Function Filter
  function runFilter(item) {
    const notCompletedItemsFilter = document.querySelectorAll('.todo-list li:not(.completed)')
    const completedItemsFilter = document.querySelectorAll('.todo-list li.completed')
    const allItemsFilter = document.querySelectorAll('.todo-list li');

    var href = item.getAttribute('href')
    href = href.split('#/')[1]

    const activeButton = document.querySelector('ul.filters a.selected')
    activeButton.classList.remove('selected')
    item.classList.add("selected")

    if (href == 'active') {

      notCompletedItemsFilter.forEach(item => {
        item.style.display = 'block';
      })
      completedItemsFilter.forEach(item => {
        item.style.display = 'none';
      })

    } else if (href == 'completed') {
      notCompletedItemsFilter.forEach(item => {
        item.style.display = 'none';
      })
      completedItemsFilter.forEach(item => {
        item.style.display = 'block';
      })
    } else if (href == 'all') {
      allItemsFilter.forEach(item => {
        item.style.display = 'block'
      })
    }
  }

  // Edit Task Double click
  items.forEach(item => {
    item.addEventListener('dblclick', event => {
      editTask(item)
    })
  })

  // Edit Task
  function editTask(item) {
    var label = item.querySelector('label');
    var editButton = item.querySelector('.edit')
    editButton.style.display = 'block'

    editButton.addEventListener('keyup', function(event) {
      label.textContent = this.value
      if (event.key == 'Enter') {
        this.style.display = 'none';
      }
    })
  }

  // Function Remove Task
  items.forEach(item => {
    item.querySelector('.destroy').addEventListener('click', function(event) {
      item.remove()
      updateCount();
    })
  })
})(window);

.todo-list li .toggle {
  cursor: pointer;
}

html,
body {
  margin: 0;
  padding: 0;
}

button {
  margin: 0;
  padding: 0;
  border: 0;
  background: none;
  font-size: 100%;
  vertical-align: baseline;
  font-family: inherit;
  font-weight: inherit;
  color: inherit;
  -webkit-appearance: none;
  appearance: none;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font: 14px 'Helvetica Neue', Helvetica, Arial, sans-serif;
  line-height: 1.4em;
  background: #f5f5f5;
  color: #4d4d4d;
  min-width: 230px;
  max-width: 550px;
  margin: 0 auto;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-weight: 300;
}

 :focus {
  outline: 0;
}

.hidden {
  display: none;
}

.todoapp {
  background: #fff;
  margin: 130px 0 40px 0;
  position: relative;
  box-shadow: 0 2px 4px 0 rgba(0, 0, 0, 0.2), 0 25px 50px 0 rgba(0, 0, 0, 0.1);
}

.todoapp input::-webkit-input-placeholder {
  font-style: italic;
  font-weight: 300;
  color: #e6e6e6;
}

.todoapp input::-moz-placeholder {
  font-style: italic;
  font-weight: 300;
  color: #e6e6e6;
}

.todoapp input::input-placeholder {
  font-style: italic;
  font-weight: 300;
  color: #e6e6e6;
}

.todoapp h1 {
  position: absolute;
  top: -155px;
  width: 100%;
  font-size: 100px;
  font-weight: 100;
  text-align: center;
  color: rgba(175, 47, 47, 0.15);
  -webkit-text-rendering: optimizeLegibility;
  -moz-text-rendering: optimizeLegibility;
  text-rendering: optimizeLegibility;
}

.new-todo,
.edit {
  position: relative;
  margin: 0;
  width: 100%;
  font-size: 24px;
  font-family: inherit;
  font-weight: inherit;
  line-height: 1.4em;
  border: 0;
  color: inherit;
  padding: 6px;
  border: 1px solid #999;
  box-shadow: inset 0 -1px 5px 0 rgba(0, 0, 0, 0.2);
  box-sizing: border-box;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.new-todo {
  padding: 16px 16px 16px 60px;
  border: none;
  background: rgba(0, 0, 0, 0.003);
  box-shadow: inset 0 -2px 1px rgba(0, 0, 0, 0.03);
}

.main {
  position: relative;
  z-index: 2;
  border-top: 1px solid #e6e6e6;
}

.toggle-all {
  width: 1px;
  height: 1px;
  border: none;
  /* Mobile Safari */
  opacity: 0;
  position: absolute;
  right: 100%;
  bottom: 100%;
}

.toggle-all+label {
  width: 60px;
  height: 34px;
  font-size: 0;
  position: absolute;
  top: -52px;
  left: -13px;
  -webkit-transform: rotate(90deg);
  transform: rotate(90deg);
}

.toggle-all+label:before {
  content: '❯';
  font-size: 22px;
  color: #e6e6e6;
  padding: 10px 27px 10px 27px;
}

.toggle-all:checked+label:before {
  color: #737373;
}

.todo-list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.todo-list li {
  position: relative;
  font-size: 24px;
  border-bottom: 1px solid #ededed;
}

.todo-list li:last-child {
  border-bottom: none;
}

.todo-list li.editing {
  border-bottom: none;
  padding: 0;
}

.todo-list li.editing .edit {
  display: block;
  width: 506px;
  padding: 12px 16px;
  margin: 0 0 0 43px;
}

.todo-list li.editing .view {
  display: none;
}

.todo-list li .toggle {
  text-align: center;
  width: 40px;
  /* auto, since non-WebKit browsers doesn't support input styling */
  height: auto;
  position: absolute;
  top: 0;
  bottom: 0;
  margin: auto 0;
  border: none;
  /* Mobile Safari */
  -webkit-appearance: none;
  appearance: none;
}

.todo-list li .toggle {
  opacity: 0;
}

.todo-list li .toggle+label {
  /*
            Firefox requires `#` to be escaped - https://bugzilla.mozilla.org/show_bug.cgi?id=922433
            IE and Edge requires *everything* to be escaped to render, so we do that instead of just the `#` - https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/7157459/
        */
  background-image: url('data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A//www.w3.org/2000/svg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%23ededed%22%20stroke-width%3D%223%22/%3E%3C/svg%3E');
  background-repeat: no-repeat;
  background-position: center left;
}

.todo-list li .toggle:checked+label {
  background-image: url('data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%22http%3A//www.w3.org/2000/svg%22%20width%3D%2240%22%20height%3D%2240%22%20viewBox%3D%22-10%20-18%20100%20135%22%3E%3Ccircle%20cx%3D%2250%22%20cy%3D%2250%22%20r%3D%2250%22%20fill%3D%22none%22%20stroke%3D%22%23bddad5%22%20stroke-width%3D%223%22/%3E%3Cpath%20fill%3D%22%235dc2af%22%20d%3D%22M72%2025L42%2071%2027%2056l-4%204%2020%2020%2034-52z%22/%3E%3C/svg%3E');
}

.todo-list li label {
  word-break: break-all;
  padding: 15px 15px 15px 60px;
  display: block;
  line-height: 1.2;
  transition: color 0.4s;
}

.todo-list li.completed label {
  color: #d9d9d9;
  text-decoration: line-through;
}

.todo-list li .destroy {
  display: none;
  position: absolute;
  top: 0;
  right: 10px;
  bottom: 0;
  width: 40px;
  height: 40px;
  margin: auto 0;
  font-size: 30px;
  color: #cc9a9a;
  margin-bottom: 11px;
  transition: color 0.2s ease-out;
}

.todo-list li .destroy:hover {
  color: #af5b5e;
}

.todo-list li .destroy:after {
  content: '×';
}

.todo-list li:hover .destroy {
  display: block;
}

.todo-list li .edit {
  display: none;
}

.todo-list li.editing:last-child {
  margin-bottom: -1px;
}

.footer {
  color: #777;
  padding: 10px 15px;
  height: 20px;
  text-align: center;
  border-top: 1px solid #e6e6e6;
}

.footer:before {
  content: '';
  position: absolute;
  right: 0;
  bottom: 0;
  left: 0;
  height: 50px;
  overflow: hidden;
  box-shadow: 0 1px 1px rgba(0, 0, 0, 0.2), 0 8px 0 -3px #f6f6f6, 0 9px 1px -3px rgba(0, 0, 0, 0.2), 0 16px 0 -6px #f6f6f6, 0 17px 2px -6px rgba(0, 0, 0, 0.2);
}

.todo-count {
  float: left;
  text-align: left;
}

.todo-count strong {
  font-weight: 300;
}

.filters {
  margin: 0;
  padding: 0;
  list-style: none;
  position: absolute;
  right: 0;
  left: 0;
}

.filters li {
  display: inline;
}

.filters li a {
  color: inherit;
  margin: 3px;
  padding: 3px 7px;
  text-decoration: none;
  border: 1px solid transparent;
  border-radius: 3px;
}

.filters li a:hover {
  border-color: rgba(175, 47, 47, 0.1);
}

.filters li a.selected {
  border-color: rgba(175, 47, 47, 0.2);
}

.clear-completed,
html .clear-completed:active {
  float: right;
  position: relative;
  line-height: 20px;
  text-decoration: none;
  cursor: pointer;
}

.clear-completed:hover {
  text-decoration: underline;
}

.info {
  margin: 65px auto 0;
  color: #bfbfbf;
  font-size: 10px;
  text-shadow: 0 1px 0 rgba(255, 255, 255, 0.5);
  text-align: center;
}

.info p {
  line-height: 1;
}

.info a {
  color: inherit;
  text-decoration: none;
  font-weight: 400;
}

.info a:hover {
  text-decoration: underline;
}


/*
        Hack to remove background from Mobile Safari.
        Can't use it globally since it destroys checkboxes in Firefox
    */

@media screen and (-webkit-min-device-pixel-ratio:0) {
  .toggle-all,
  .todo-list li .toggle {
    background: none;
  }
  .todo-list li .toggle {
    height: 40px;
  }
}

@media (max-width: 430px) {
  .footer {
    height: 50px;
  }
  .filters {
    bottom: 10px;
  }
}

hr {
  margin: 20px 0;
  border: 0;
  border-top: 1px dashed #c5c5c5;
  border-bottom: 1px dashed #f7f7f7;
}

.learn a {
  font-weight: normal;
  text-decoration: none;
  color: #b83f45;
}

.learn a:hover {
  text-decoration: underline;
  color: #787e7e;
}

.learn h3,
.learn h4,
.learn h5 {
  margin: 10px 0;
  font-weight: 500;
  line-height: 1.2;
  color: #000;
}

.learn h3 {
  font-size: 24px;
}

.learn h4 {
  font-size: 18px;
}

.learn h5 {
  margin-bottom: 0;
  font-size: 14px;
}

.learn ul {
  padding: 0;
  margin: 0 0 30px 25px;
}

.learn li {
  line-height: 20px;
}

.learn p {
  font-size: 15px;
  font-weight: 300;
  line-height: 1.3;
  margin-top: 0;
  margin-bottom: 0;
}

#issue-count {
  display: none;
}

.quote {
  border: none;
  margin: 20px 0 60px 0;
}

.quote p {
  font-style: italic;
}

.quote p:before {
  content: '“';
  font-size: 50px;
  opacity: .15;
  position: absolute;
  top: -20px;
  left: 3px;
}

.quote p:after {
  content: '”';
  font-size: 50px;
  opacity: .15;
  position: absolute;
  bottom: -42px;
  right: 3px;
}

.quote footer {
  position: absolute;
  bottom: -40px;
  right: 0;
}

.quote footer img {
  border-radius: 3px;
}

.quote footer a {
  margin-left: 5px;
  vertical-align: middle;
}

.speech-bubble {
  position: relative;
  padding: 10px;
  background: rgba(0, 0, 0, .04);
  border-radius: 5px;
}

.speech-bubble:after {
  content: '';
  position: absolute;
  top: 100%;
  right: 30px;
  border: 13px solid transparent;
  border-top-color: rgba(0, 0, 0, .04);
}

.learn-bar>.learn {
  position: absolute;
  width: 272px;
  top: 8px;
  left: -300px;
  padding: 10px;
  border-radius: 5px;
  background-color: rgba(255, 255, 255, .6);
  transition-property: left;
  transition-duration: 500ms;
}

@media (min-width: 899px) {
  .learn-bar {
    width: auto;
    padding-left: 300px;
  }
  .learn-bar>.learn {
    left: 8px;
  }
}

.destroy {
  cursor: pointer;
}

<!-- <link rel="stylesheet" href="node_modules/todomvc-common/base.css"> -->
<!-- <link rel="stylesheet" href="node_modules/todomvc-app-css/index.css"> -->

<section class="todoapp">
  <header class="header">
    <h1>todos</h1>
    <input class="new-todo" placeholder="What needs to be done?" autofocus>
  </header>
  <!-- This section should be hidden by default and shown when there are todos -->
  <section class="main">
    <input id="toggle-all" class="toggle-all" type="checkbox">
    <label for="toggle-all">Mark all as complete</label>
    <ul class="todo-list">
      <!-- These are here just to show the structure of the list items -->
      <!-- List items should get the class `editing` when editing and `completed` when marked as completed -->
      <li class='completed'>
        <div class="view">
          <input class="toggle" checked type="checkbox">
          <label>Taste JavaScript</label>
          <button class="destroy"></button>
        </div>
        <input class="edit" value="Taste JavaScript">
      </li>
      <li>
        <div class="view">
          <input class="toggle" type="checkbox">
          <label>Refactoring Code</label>
          <button class="destroy"></button>
        </div>
        <input class="edit" value="Refactoring Code">
      </li>
      <li>
        <div class="view">
          <input class="toggle" type="checkbox">
          <label>Rewrite app to react</label>
          <button class="destroy"></button>
        </div>
        <input class="edit" value="Rewrite app to react">
      </li>
    </ul>
  </section>
  <!-- This footer should hidden by default and shown when there are todos -->
  <footer class="footer">
    <!-- This should be `0 items left` by default -->
    <span class="todo-count"><strong>0</strong> item left</span>
    <!-- Remove this if you don't implement routing -->
    <ul class="filters">
      <li>
        <a class="selected" href="#/all">All</a>
      </li>
      <li>
        <a href="#/active">Active</a>
      </li>
      <li>
        <a href="#/completed">Completed</a>
      </li>
    </ul>
    <!-- Hidden if no completed items are left ↓ -->
    <button class="clear-completed">Clear completed</button>
  </footer>
</section>
<footer class="info">
  <p>Double-click to edit a todo</p>
  <p>Enter to add/edit task</p>

</footer>
<!-- Scripts here. Don't remove ↓ -->
<!-- <script src="node_modules/todomvc-common/base.js"></script> -->

Answer 1

User interaction issue

There is a flaw with the double-click to edit mechanism - it only works for existing items, but for newly added items, the double click handler is not registered. The same is true for the destroy links.

Instead of adding a click handler to each list item, event delegation could be used to add a click handler to the list and delegate the editing event to the list item.

JS

selecting elements

I know CertainPerformance has already touched on the code to select elements. For the selection of list items, event delegation could be achieved by converting these lines:

const todoList = document.getElementsByClassName('todo-list')[0]
const items = document.querySelectorAll('.todo-list li')

to this:

const todoList = document.getElementsByClassName('todo-list')[0];
const items = todoList.getElementsByTagName('li'); // <- active collection

Note that getElementsByTagName() returns a live HTMLCollection¹ so there is no need to re-query the list after items are added or removed... and to iterate over the items, they can be put into an array using the spread operator:

[...items].forEach(...)

comparison operators

It is recommended by many to use strict equality when comparing values - that way there is no need to have types converted. For example, in this line in runFilter:

if (href == 'active') {

href comes from var href = item.getAttribute('href') and that method returns a string or null. Thus there is no need for type coercion.

Repeated methods to update element display properties

That runFilter function has multiple forEach() loops with arrow functions like this:

item => {
  item.style.display = 'block';
}

The repeated functions could be abstracted to named functions to avoid redundancies.

Additionally, instead of setting the style, the classList methods like add() and remove() could be used instead - with the CSS class hidden.

CSS

There is a ruleset for html and body:

html,
body {
  margin: 0;
  padding: 0;
} 

then later on there is one for body:

body { 

and it has this:

  margin: 0 auto;

That seems excessive... one or both of those could be removed.

margin syntax

The current CSS contains this:

.todoapp {
  background: #fff;
  margin: 130px 0 40px 0;

The margin syntax could be converted from /* top | right | bottom | left */ to /* top | horizontal | bottom */.

  margin: 130px 0 40px;

Answer 2

You have

const input = document.getElementsByClassName('new-todo')[0]

When selecting only a single element, it's a bit more appropriate and terser to use querySelector instead:

const input = document.querySelector('.new-todo');

I notice that sometimes you're using semicolons, and sometimes you're not. Unless you're an expert, I'd recommend using them, else ASI may trip you up, resulting in hard-to-understand bugs. Consider using a linter to enforce your preferred style.

You have

var string = input.value;
// ...
li.innerHTML = `
    <div class="view">
        <input class="toggle" type="checkbox" />
        <label>${string}</label>
        <button class="destroy"></button>
    </div>
    <input class="edit" value="${string}">
`;

Don't concatenate HTML strings from user input; if the user accidentally uses characters with HTML syntax, like <, this can result in a unexpected appearance and unexpected elements in the DOM. It can also run arbitrary code, which could be a security risk (imagine if another user said: "Try putting this in as a todo input, you won't believe what happens next!" and then the victim gets their login info stolen).

Instead, once you have a reference to the container of the text, assign to the container's textContent:

var string = input.value;

if (e.key == 'Enter') {
  const li = document.createElement('li')
  li.innerHTML = `
      <div class="view">
          <input class="toggle" type="checkbox" />
          <label></label>
          <button class="destroy"></button>
      </div>
      <input class="edit" value="${string}">
  `;
  li.querySelector('label').textContent = string;

You have a var there, but you're also using const. If you're going to write in ES2015 with const and let, that's great - but, best to use it everywhere. (If you're writing in ES2015, never use var. Linting rule)