Building a todo application
The obligatory todo app.
Last updated
Was this helpful?
The obligatory todo app.
Last updated
Was this helpful?
Todo applications are overdone, but it is hard to argue that they do not showcase some common Javascript framework or library features. For example, working with collections of data, binding to events, calling functions, and mutating values.
A todo application comprised of the following features:
Displays a list of one or more todo items
Todo items can be completed (a strikethrough will denote a completed todo)
Todo items can be deleted
Todo items can be added and will be pushed to the top of the list.
See what you are getting yourself into before you continue. There is a working example of this application .
Before going any further, you should be familiar with some basic Aurelia concepts and some fundamental Javascript ones. While these are not hard prerequisites, please know that some concepts used in this tutorial out of context might be confusing or difficult to understand.
You have familiarized yourself with the .
You have familiarized yourself with .
You are familiar with . You don't need to be a master of it; you just need to be familiar with its existence and why it matters in Aurelia.
When creating a new Aurelia 2 application, using the CLI is considered best practice. You can type npx makes aurelia to do this, but we will give you the shorthand syntax to do this faster for this tutorial.
Unlike other tutorials in the Aurelia 2 docs, we will not use any CSS preprocessors, only plain old Javascript instead of TypeScript (Aurelia can support both). This tutorial highlights just how basic an Aurelia application can be: CSS, Javascript and HTML.
Because this is an Aurelia tutorial, we are not going to delve into the CSS. To provide you with a beautiful todo list, all styling is provided.
Copy and paste the following CSS and add it into my-app.css, which should have been created as part of the CLI generation (if not, create it). This just gives us a nice font and some CSS grid styling for the layout to make our todo application look like a proper app and not a backyard DIY job.
The todo component will be the main part of our application. It will contain the logic and markup for our entire app, with a singular child component for the todo items themselves being the only other component (we will create that one next).
Create three new files inside of a folder called components
todo-component.html
todo-component.js
todo-component.css
The todo-component.html file is our view, todo-component.js is our view model, and todo-component.css is the styling that gets automatically included because it matches our component name.
Open up todo-component.js first as this will contain the most code and some example todos as well:
Let's go over this view model code line-by-line:
We export a class, which is the name of our component
Line 2: We create an empty string called todo. This is where any todos we author are stored temporarily
Line 4: an array of todo items (and any new ones that get added)
Line 15: newTodo is a function that gets called on keypress in the view
We check if the key pressed is enter (keycode 13)
If it is, we unshift our todo into the todos array
We then reset the todo property
Line 21: Aurelia will prevent all events by default when you bind to them, so we need to return true outside of our if statement or typing will break in our input field
Line 24: deleteTodo will remove a todo from our todos array and is passed an index
We call Array.splice on the todos array and tell it we want to delete one item
Believe it or not, this view model code forms the basis for adding and deleting todos. The code would be much smaller if we didn't have example todos in there.
The view is the most simple part of our application. Inside of todo-component.html add in the following HTML, and then we'll explain what is going on.
Line 1: importing an as-of-yet nonexistent todo-item component
Line 8: we define a text input field and bind its value to todo and also a keypress.trigger to listen to keyboard events (we want to know when the user hits enter)
Line 12: using a repeater, we are looping over the todos in our view model and binding them onto the todo-item element
todo.bind="todo" we have a bindable property defined on the todo-item element called todo
index.bind="$index" another bindable property defined in the todo-item element, we pass in the current loop index denoted by its special simple prefix $index
delete-todo.bind="() => deleteTodo($index)" this is a callback function that will call deleteTodo when a todo is deleted from inside of the todo-item
Let's now quickly add in some styling for our todo component. Open up todo-component.css and add in the following. This will make our todo items pretty and sit nicely. We are using CSS Grid for this part.
We have created our main todo component, but you might have noticed we were importing a file that doesn't exist yet todo-item.html. Let's create that right now.
For this component, we are going to be creating an HTML-only component. It means it'll just be HTML. No view model needed:
Lines 1,2 & 3: The bindable attribute allows us to specify bindable properties for our custom element. This allows us to bind to these values and read them inside of our view. The deleteTogo bindable is interesting because it is bindable for a function that gets passed in.
Line 5: we use the .class binding to add a class to our element of completed if the todo.completed property is true or remove it if it's false.
Line 6: We bind the native checkbox checked event to the completed property, which sets it to true or false
Line 7: We are making our paragraph element a contenteditable element, which allows it to be edited (it doesn't save, but we can temporarily edit our text). We also display the text value using our interpolation ${}
Line 8: Lastly, we have a click.trigger to call our passed-in deleteTodo bindable function callback when clicked
Even though our todo-item.html component is HTML only and has no view model, Aurelia's default conventions still work. This means creating a CSS file called todo-item.css it will automatically be included when we reference our element.
Create a new file todo-item.css in the components directory and add the following:
To round it all off, let's open up my-app.html and add the following:
This forms the basis of our application. The todo-component custom element is the main application container for our app. We import it and then reference it by its HTML tag name.
Now, let's run the app: npm start on the command line and wait for the browser to open. You should see a functioning todo list application. It should look something like the following screenshot. Type into the todo input field and hit enter to see it works.
If you missed the link initially, a working example can be seen . The code for this tutorial can also be found .
