JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div class="container">
      <p>
        <label for="new-task">Add Item</label><input id="new-task" type="text"><button>Add</button>
      </p>
      
      <h3>Todo</h3>
      <ul id="incomplete-tasks">
        <li><input type="checkbox"><label>Pay Bills</label><input type="text"><button class="edit">Edit</button><button class="delete">Delete</button></li>
        <li><input type="checkbox"><label>Go Shopping</label><input type="text" value="Go Shopping"><button class="edit">Edit</button><button class="delete">Delete</button></li>
        
      </ul>
      
      <h3>Completed</h3>
      <ul id="completed-tasks">
        <li><input type="checkbox" checked><label>See the Doctor</label><input type="text"><button class="edit">Edit</button><button class="delete">Delete</button></li>
      </ul>
    </div>


  </body>

CSS

/* Basic Style */
*:focus {
    outline: 1px solid rgba(63, 138, 191, 1);
}

body {
    background: #fff;
    color: #333;
    font-family: Lato, sans-serif;
}
.container {
    display: block;
    width: 400px;
    margin: 100px auto 0;
}
ul {
    margin: 0;
    padding: 0;
}
li * {
    float: left;
}
li, h3 {
    clear:both;
    list-style:none;
}
input, button {

    /*outline: none;*/
}
button {
    background: none;
    border: 0px;
    color: #888;
    font-size: 15px;
    width: 60px;
    margin: 10px 0 0;
    font-family: Lato, sans-serif;
    cursor: pointer;
}
button:hover {
    color: #333;
}
/* Heading */
h3,
label[for='new-task'] {
    color: #333;
    font-weight: 700;
    font-size: 15px;
    border-bottom: 2px solid #333;
    padding: 30px 0 10px;
    margin: 0;
    text-transform: uppercase;
}
input[type="text"] {
    margin: 0;
    font-size: 18px;
    line-height: 18px;
    height: 18px;
    padding: 10px;
    border: 1px solid #ddd;
    background: #fff;
    border-radius: 6px;
    font-family: Lato, sans-serif;
    color: #888;
}
input[type="text"]:focus {
    color: cornflowerblue;
    border-color: cornflowerblue;
}

/* New Task */
label[for='new-task'] {
    display: block;
    margin: 0 0 20px;
}
input#new-task {
    float: left;
    width: 318px;
}
p > button:hover {
    color: #0FC57C;
}

/* Task list */
li {
    overflow: hidden;
    padding: 20px 0;
    border-bottom: 1px solid #eee;
}
li > input[type="checkbox"] {
    margin: 0 10px;
    position: relative;
    top: 15px;
}
li > label {
    font-size: 18px;
    line-height: 40px;
    width: 237px;
    padding: 0 0 0 11px;
}
li >  input[type="text"] {
    width: 226px;
}
li > .delete:hover {
    color: #CF2323;
}

/* Completed */
#completed-tasks label {
    text-decoration: line-through;
    color: #888;
}

#completed-tasks button.edit {
    display: none;
}

/* Edit Task */
ul li input[type=text] {
    display:none;
}

ul li.editMode input[type=text] {
    display:block;
    color:...

JavaScript

/**
 * @project : To Do List w/ JavaScript
 * @objective : Code the user interaction for the form. The form must be able to add, edit, remove and complete tasks on the list.
 */

//Variables
var taskInput = document.getElementById('new-task'); //new-task
var addTaskButton = document.getElementsByTagName('button')[0]; //first button BUT WHY NOT JUST ASSIGN IT AN ID?!?!?!??!
var incompleteTasksHolder = document.getElementById('incomplete-tasks'); //ul#incomplete-tasks;
var completedTasksHolder = document.getElementById('completed-tasks'); //ul#completed-tasks;

//New Task List Item
var createNewTaskEl = function(taskString){
    //create list item
    var listItem = document.createElement('li');

    //input checkbox
    var checkbox = document.createElement('input'); //checkbox
    //label
    var label = document.createElement('label');
    //edit input text
    var editInput = document.createElement('input'); //text
    //button.edit
    var editBtn = document.createElement('button');
    //button.delete
    var deleteBtn = document.createElement('button');

    //each element needs modifying
    checkbox.type= 'checkbox';
    editInput.type= 'text';

    editBtn.innerText = 'Edit';
    editBtn.className = 'edit';
    deleteBtn.innerText = 'Delete';
    deleteBtn.className = 'delete';

    label.innerText = taskString;

    //each element has to be appended
    listItem.appendChild(checkbox);
    listItem.appendChild(label);
    listItem.appendChild(editInput);
    listItem.appendChild(editBtn);
    listItem.appendChild(deleteBtn);
    return listItem;
};


//Add Task
var addTask = function(){
    //console.log('Add task');
    //Create a task -- new list item w/ text from #new-task and the elements inside
    //make sure the task has something there
    if(taskInput.value.length > 4){
        var listItem = createNewTaskEl(taskInput.value);
        incompleteTasksHolder.appendChild(listItem); //Append to Incomplete Task Handler
        bindTaskEvents(listItem,...