JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.10.3/themes/redmond/jquery-ui.min.css">
<script src="https://jquery-elastic.googlecode.com/svn-history/r37/trunk/jquery.elastic.js"></script>
<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.11.0/jquery-ui.min.js"></script>
<!DOCTYPE html>
<div id="bar">
    <h4>Tasks</h4>
    
    <span id="actions">
        <button id="undo" disabled>Undo</button>
        <!--<input type="image" src="http://i.imgur.com/fyCSlvW.png" />-->
        <button id="redo" disabled>Redo</button>
    </span>
</div>

<p id="info"></p>
<div id="todo_list_container">
    <ul id="todo_items">
    </ul>
    <span id="add_todo">
        <span id="add_button_container"><button id="add" disabled><span id="small">+</span><br/><span id="smaller">ADD</span></button></span>
        <span id="new_item_textarea_container"><textarea id="new_todo_item" placeholder="Create new task" spellcheck="true"></textarea></span>
        <span id="star_container"><input type="checkbox" id="star" /><label>Star</label></span>
    </span>
</div>

CSS

body{
    font-family: "Arial";
    font-size: 62.5%;
}

h4{
    text-decoration: none;
    display: inline-block;
    margin-top: 2rem;        /* = 20px */
    color: white;
    margin-left: 1.5rem;
    font-size: 1.8rem;
    line-height: 0px;
}

#actions {
    float: right;
    margin: 1.5rem 1.5rem 1.2rem auto;
    /*vertical-align: middle;*/
    /*line-height: 3.5rem;*/
}

#undo:disabled{
    /*background: url("http://i.imgur.com/fyCSlvW.png");*/
}

#bar{
    background-color: #4196C2;
    margin: 0rem;
    padding: 0rem;
}

.item_content{
    display: inline;
    font-size: 1.7rem;
    word-break:break-all;
}

#todo_list_container{
    width: 100%;
    /*border: .1em solid black;*/
    /*min-width: 42rem;*/
}

#todo_items{
    /*border: .1em solid red;
    display: inline-block;*/
}

ul
{
    list-style-type: none;
}

label{
    float: right;
}

.star{
    float: right;
}

#add, #star, label, .done{
    vertical-align: middle;
}

textarea{
    width: 60%;
    resize: none;
    
    border: 0px solid red;
    overflow: auto;
    outline: none;
    
    -webkit-box-shadow: none;
    -moz-box-shadow: none;
    box-shadow: none;
    
    font-family: "Arial";
    font-size: 1.5rem; 
    
    vertical-align: middle;
    
    min-width: 0rem;
}

.done, #add{
    height: 4rem;
    width: 4rem;
    border-radius: 50%;
    color: #7CB8D4;
    border: 0.1rem solid #7CB8D4;
    background-color: #E7F7FF;
    outline: none;
    line-height:80%;
    margin-right: 1rem;
}

.done:hover{
    border: 0.3rem solid #7CB8D4;
}

#add_todo{
    width: 100%;
    /*border: 1px solid yellow;*/
}

#add_button_container{
    width: 20%;
    /*border: 1px solid blue;*/
}

#new_item_textarea_container{
    width: 70%;
    /*border: 1px solid blue;*/
}

#star_container{
    width: 10%;
    /*border: 1px solid blue;*/
}

#add{
    color: #E7F7FF;
    background-color: #7CB8D4;
    margin-left: 1rem;
}

#add:disabled {
    opacity: 0.5;
}

#small{
    font-size: 1.2rem;
    line-height:...

JavaScript

$(function(){    
    
    // declare an object literal
    var todo_item = {
        content: "",        // default content
        starred: false,     // default star value
        undoStack: [],
        redoStack: [],
        addItem: function(){
            // collect new item data
            todo_item.content = $("#new_todo_item").val();
            todo_item.starred = $("#star").prop('checked');
            addItem(todo_item);
        },
        toggleStar: function(element, addToUndoStack){
            toggleStar(element, addToUndoStack);
        },
        editItem: function(element, addToUndoStack){
            editItem(element, addToUndoStack);
        },
        markAsDone: function(element){        
            markAsDone(element);
        },
        renumberItems: function(){        // re-number items after populating from localStorage, marking as done and drag/drop
            renumberItems();
        },
        checkLocalStorageBrowserSupport: function(){
            checkLocalStorageBrowserSupport();
        },
        checkLocalStorageExistingData: function(){
            checkLocalStorageExistingData();
        },
        getLocalStorageData: function(){
            getLocalStorageData();
        },
        setLocalStorageData: function(data){
            setLocalStorageData(data);
        },
        undo: function(undoStack){
            undo(undoStack);
        },
        redo: function(redoStack){
            redo(redoStack);
        },
        tweakMinorUIStuff: function(){
            tweakMinorUIStuff();
        }
    };
    
    // setup the UI
    todo_item.checkLocalStorageBrowserSupport();
    todo_item.checkLocalStorageExistingData();
    todo_item.tweakMinorUIStuff();
    todo_item.renumberItems();
    
    // setup event listeners
    $(document).on("click", "#add",          function(){ todo_item.addItem();                            });
    $(document).on("click", ".star",         function(){ todo_item.toggleStar(this, true);     ...