REScala • TodoMVC

REScala is a Scala library for functional reactive programming on the JVM and the Web. It provides a rich API for event stream transformations and signal composition with managed consistent up-to-date state and minimal syntactic overhead. It supports concurrent and distributed programs.

REScala — www.rescala-lang.com

Implementation

We implemented most of the TodoMVC specification. Especially interesting is the use of reactive signals to generate html-elements, which update automatically with the sync, and the ability to persist state into localStorage automatically, by saving all signals values.

• New todos are entered in top input, which is autofocused. Enter clears input, input is trimmed, and empty todos are not allowed.
• Hide footer when there are no todos.
• Mark-all button makes toggles every todos done state.
• Clicking todo checkbox toggles their done state.
• Double clicking a todo label turns it into editing mode. Editing hides checkbox and deletion button. blur and enter end editing.
• On changes, input is trimmed. Empty todos shall be deleted.
• Deletion button is shown on hovering over todos.
• Todo counter is pluralized correctly: 0 items, 1 item, 2 items, ... .
• The clear-completed button is only visible when there are todos.
• Todo state persists using localStorage over consecutive page visits.

We have not implemented the following things:

• To integrate seamlessly into scala development, we use sbt for dependency management instead of npm.
• If all todos get marked done, the Mark-done button should show this.
• Double clicking focused the editing input.
• We have not implemented routing and the related todo filters.
• Escaping the input shall cancel editing, restore previous value.

Running

You need sbt beforehand. Last tested using sbt 1.9.0.

Run with:

$ sbt deploy                       # get scala dependencies and compile scala to js
$ firefox target/index.html        # open generated file in browser