Building a To-Do List with jQuery and Local Storage

We all have those days when we have a lot of things to accomplish, but no way to know if we will complete all of them. In these situations, a to-do list is extremely helpful. There are great mobile apps, online tools, and even WordPress plugins which perform this task, but have you ever wondered how long it would take to create one by yourself? In this tutorial, we will create a basic to-do list. Tasks will fall into one of three categories – pending, in progress, and completed. Our application will allow new tasks to be created, which go into the pending category by default. Tasks can easily be moved between categories using drag and drop technology. Of course, tasks can also be deleted.

Prerequisites

The following libraries are used in this project.

jQuery 1.10.2
jQuery UI 1.10.3
Bootstrap 2.2.2

Creating the Markup and CSS

Let’s create the basic look and feel of the application before adding the functionality via JavaScript.

<div class="task-list" id="pending">
  <h3>Pending</h3>
  <!-- Sample task added manually to check look -->
  <div class="todo-task">
    <div class="task-header">Sample Header</div>
    <div class="task-date">25/06/1992</div>
    <div class="task-description">Lorem Ipsum Dolor Sit Amet</div>
  </div>
</div>

<div class="task-list" id="inProgress">
  <h3>In Progress</h3>
</div>

<div class="task-list" id="completed">
  <h3>Completed</h3>
</div>

<div class="task-list">
  <h3>Add a task</h3>
  <form id="todo-form">
    <input type="text" placeholder="Title" />
    <textarea placeholder="Descrtipion"></textarea>
    <input type="text" placeholder="Due Date (dd/mm/yyyy)" />
    <input type="button" class="btn btn-primary" value="Add Task" />
  </form>

  <input type="button" class="btn btn-primary" value="Clear Data" />

  <div id="delete-div">Drag Here to Delete</div>
</div>

Next, add some styling to the elements using the following CSS.

.task-list {
  width: 250px;
  float: left;
  margin: 0 5px;
  background-color: #e3e3e3;
  min-height: 240px;
  border-radius: 10px;
  padding-bottom: 15px;
}

.task-list input, .task-list textarea {
  width: 240px;
  margin: 1px 5px;
}

.task-list input {
  height: 30px;
}

.todo-task {
  border-radius: 5px;
  background-color: #fff;
  width: 230px;
  margin: 5px;
  padding: 5px;
}

.task-list input[type="button"] {
  width: 100px;
  margin: 5px;
}

.todo-task > .task-header {
  font-weight: bold;
}

.todo-task > .task-date {
  font-size: small;
  font-style: italic;
}

.todo-task > .task-description {
  font-size: smaller;
}

h3 {
  text-align: center;
}

#delete-div {
  background-color: #fff;
  border: 3px dotted #000;
  margin: 10px;
  height: 75px;
  line-height: 75px;
  text-align: center;
}

Our static to-do page should look like the following image. Todo list demo

Defining the JavaScript Constants

Throughout this tutorial, we will be referring to certain constants to avoid hard coding values. These constants are shown below.

var defaults = {
  // CSS selectors and attributes that would be used by the JavaScript functions
  todoTask: "todo-task",
  todoHeader: "task-header",
  todoDate: "task-date",
  todoDescription: "task-description",
  taskId: "task-",
  formId: "todo-form",
  dataAttribute: "data",
  deleteDiv: "delete-div"
}, codes = {
  "1" : "#pending", // For pending tasks
  "2" : "#inProgress",
  "3" : "#completed"
};

Creating Tasks

Tasks are created using the following JavaScript function.

// Add Task
var generateElement = function(params) {
  var parent = $(codes[params.code]),
      wrapper;

  if (!parent) {
    return;
  }

  wrapper = $("<div />", {
    "class" : defaults.todoTask,
    "id" : defaults.taskId + params.id,
    "data" : params.id
  }).appendTo(parent);

  $("<div />", {
    "class" : defaults.todoHeader,
    "text": params.title
  }).appendTo(wrapper);

  $("<div />", {
    "class" : defaults.todoDate,
    "text": params.date
  }).appendTo(wrapper);

  $("<div />", {
    "class" : defaults.todoDescription,
    "text": params.description
  }).appendTo(wrapper);
};

The following code sample shows how a single task is generated.

generateElement({
  id: "123",
  code: "1",
  title: "My Uber Important Task",
  date: "5/2/2014",
  description: "I have to do a lot of steps to implement this task!"
});

Deleting Tasks

Removing tasks is fairly simple, and can be accomplished using the following function.

var removeElement = function(params) {
  $("#" + defaults.taskId + params.id).remove();
};

Saving Tasks in Local Storage

The tasks we create could be stored using a database, cookies, or a number of other technologies. However, in this application we’re going to use HTML5’s local storage for its simplicity. In JavaScript, the variable localStorage stores all of this data. The following code sample shows how the to-do list data is retrieved from local storage.

var data = JSON.parse(localStorage.getItem("todoData"));

Each task would be stored within the data variable. An example task object is shown below.

{
  id : id, // Unique ID; timestamp is used here
  code: "1", // Code identifying the category
  title: title, // Title of the task
  date: date, // Due date
  description: description // Description of the task
}

We update the saved data in local storage using the following code.

localStorage.setItem("todoData", JSON.stringify(data));

Submitting the To-Do Form

When the to-do form is submitted, a new task is created and added to local storage, and the contents of the page are updated. The following function implements this functionality.

var addItem = function() {
  var inputs = $("#" + defaults.formId + " :input"),
      errorMessage = "Title can not be empty",
      id, title, description, date, tempData;

  if (inputs.length !== 4) {
    return;
  }

  title = inputs[0].value;
  description = inputs[1].value;
  date = inputs[2].value;

  if (!title) {
    generateDialog(errorMessage);
    return;
  }

  id = new Date().getTime();

  tempData = {
    id : id,
    code: "1",
    title: title,
    date: date,
    description: description
  };

  // Saving element in local storage
  data[id] = tempData;
  localStorage.setItem("todoData", JSON.stringify(data));

  // Generate Todo Element
  generateElement(tempData);

  // Reset Form
  inputs[0].value = "";
  inputs[1].value = "";
  inputs[2].value = "";
};

Implementing Drag and Drop

jQuery UI provides drag and drop functionality. We need to make each task draggable and each of the three categories droppable. To delete a task, we need to hide the delete area by default, and show it during the time an item is being dragged. Therefore, we first modify the generateElement() function slightly to first make the to-do list items draggable, and then make the delete area visible when the item is being drug.

$("." + defaults.todoTask).draggable();

// Add Task
var generateElement = function(params) {
  wrapper.draggable({
    start: function() {
      $("#" + defaults.deleteDiv).show();
    },
    stop: function() {
      $("#" + defaults.deleteDiv).hide();
    }
  });
...
};

Secondly, we need to add the droppable() function to each of the categories as the elements are supposed to be dropped in any one of the three areas.

// Adding drop function to each category of task
$.each(codes, function(index, value) {
  $(value).droppable({
    drop: function(event, ui) {
      var element = ui.helper,
          css_id = element.attr("id"),
          id = css_id.replace(options.taskId, ""),
          object = data[id];

      // Removing old element
      removeElement(object);

      // Changing object code
      object.code = index;

      // Generating new element
      generateElement(object);

      // Updating Local Storage
      data[id] = object;
      localStorage.setItem("todoData", JSON.stringify(data));

      // Hiding Delete Area
      $("#" + defaults.deleteDiv).hide();
    }
  });
});

Thirdly, we need to add some code to delete tasks when they are dropped in the delete area.

// Adding drop function to delete div
$("#" + options.deleteDiv).droppable({
  drop: function(event, ui) {
    var element = ui.helper,
        css_id = element.attr("id"),
        id = css_id.replace(options.taskId, ""),
        object = data[id];

    // Removing old element
    removeElement(object);

    // Updating local storage
    delete data[id];
    localStorage.setItem("todoData", JSON.stringify(data));

    // Hiding Delete Area
    $("#" + defaults.deleteDiv).hide();
  }
});

Conclusion

The final code is available on GitHub. You can also check out the project’s live demo.

Frequently Asked Questions (FAQs) about Building a List with jQuery and Local Storage

How can I add a delete button to each item in the to-do list?

Adding a delete button to each item in the to-do list can be achieved by appending a button element to each list item during its creation. You can use the jQuery append() method to add a button element with a class of ‘delete’. Then, you can use jQuery’s on() method to attach a click event handler to the delete button, which removes the parent list item when clicked. Remember to also remove the item from local storage.

How can I edit an item in the to-do list?

To edit an item in the to-do list, you can add an ‘edit’ button similar to the ‘delete’ button. When this button is clicked, you can replace the text of the list item with an input field containing the current text. The user can then edit the text and press ‘Enter’ to save the changes. Don’t forget to update the item in local storage as well.

How can I mark an item as completed?

Marking an item as completed can be done by toggling a ‘completed’ class on the list item. You can attach a click event handler to the list item that adds or removes the ‘completed’ class when clicked. You can use CSS to style completed items differently, such as striking through the text. Remember to update the item’s status in local storage.

How can I sort the items in the to-do list?

Sorting the items in the to-do list can be done using jQuery’s sort() method. You can sort the items based on their text, or based on their completed status. After sorting the items, you can clear the list and add the items back in the sorted order. Don’t forget to update the order of items in local storage.

How can I filter the items in the to-do list?

Filtering the items in the to-do list can be done by adding an input field that the user can type into. You can then use jQuery’s filter() method to hide the items that do not match the user’s input. Remember to update the visibility of items in local storage.

How can I save the to-do list to a file?

Saving the to-do list to a file can be done by converting the list to a JSON string using JSON.stringify(), and then using the download attribute of the anchor element to download the string as a file. The user can then load the list from the file by reading the file and parsing the JSON string using JSON.parse().

How can I load the to-do list from a file?

Loading the to-do list from a file can be done by using the FileReader API to read the file. The file can be selected using an input element of type ‘file’. After reading the file, you can parse the JSON string using JSON.parse() and add the items to the list and to local storage.

How can I add categories to the to-do list?

Adding categories to the to-do list can be done by adding a select element to the form used to add new items. The select element can contain option elements for each category. When a new item is added, the selected category can be stored as a data attribute on the list item. You can then filter the items based on their category.

How can I add due dates to the to-do list?

Adding due dates to the to-do list can be done by adding a date input field to the form used to add new items. When a new item is added, the selected date can be stored as a data attribute on the list item. You can then sort or filter the items based on their due date.

How can I add priorities to the to-do list?

Adding priorities to the to-do list can be done by adding a select element to the form used to add new items. The select element can contain option elements for each priority level. When a new item is added, the selected priority can be stored as a data attribute on the list item. You can then sort or filter the items based on their priority.