Welcome to Bolero: F# on WebAssembly!
Bolero is a set of free and open-source libraries and tools to write WebAssembly applications in F#. With it, you can write fully dynamic client-side web applications from the comfort of a strongly-typed functional language, all with great performance.
Bolero is built on top of Blazor and adds a lot of features designed specifically to work in F#:
You can develop Bolero applications on Windows, OSX or Linux. It only has one prerequisite: the .NET Core SDK, version 3.0-preview5 or newer.
The easiest way to get started is to use Bolero's dotnet template. To install it, run the following command:
dotnet new -i Bolero.Templates
Then, you can create a new Bolero application:
dotnet new bolero-app -o HelloWorld
This will create a new folder
HelloWorld and create an application inside it. The template has additional options, described at its home page. You can run it with:
cd HelloWorld dotnet run -p src/HelloWorld.Server
This will start the server and run the following minimal application at
The solution you just created comprises two projects.
src/HelloWorld.Client is the project that gets compiled to WebAssembly, and contains your client-side code.
Main.fs contains the main body of the page. This is where the meat of the application is: as you develop, you will mostly be coding here and in new files referenced from here.
wwwroot/ contains static content. In particular,
index.html is the actual page that is served. It contains a script reference to
blazor.webassembly.js, which in turn loads your application.
If you want to add styles and images to your application, this is the folder to put them.
Startup.fs sets up Blazor to get the application started. You will rarely need to touch it: essentially only to set up remoting, if you want to use it.
src/HelloWorld.Server is an ASP.NET Core application that serves as the host. This project is optional: if you pass
--server=false when creating the solution with
dotnet new, then it will not be created. Note however that it is necessary for templating hot reloading and remoting.
Startup.fs, similarly to its client counterpart, sets up ASP.NET Core to get the server started.