First application: Hello World

Build a small Mojara web application. You will create it, write the handler, start the server, and change what the browser displays.

1. Create an application

mojara new hello-world web
cd hello-world

The first command creates a web application named hello-world. The second command enters that application.

2. Write Hello World

Open app.mojo and replace the starter code with this example:

from mojara import App, Request, Response

def home(req: Request) -> Response:
    return Response.html("<h1>Hello, World!</h1>")

def main() raises:
    var app = App()
    app.get("/", home)
    app.run(port=8000)

What this code does: App creates the web app. home is the function that builds the HTML response. app.get("/", home) connects the root URL to that function. app.run(port=8000) starts the HTTP server.

3. Run the application

mojara dev

Open http://127.0.0.1:8000/ in a browser. The page displays:

Hello, World!

If Mojara prints a different listening port, use that address.

4. Change the response

Edit the HTML inside home:

def home(req: Request) -> Response:
    return Response.html("<h1>My first Mojara website</h1>")

Save your changes. Once the development server rebuilds, reload the browser. Your new heading appears.

5. Build and start

Stop the development server with Ctrl+C, then:

mojara build
mojara start

build compiles the application. start starts the compiled server.

Next step

Learn how to add additional pages, serve JSON, and handle POST requests in Routing.