The default Sapper template. To clone it and get started:
npx degit sveltejs/sapper-template my-app cd my-app npm install # or yarn! npm run dev
Open up localhost:3000 and start clicking around.
Sapper expects to find three directories in the root of your project —
In your service-worker.js file, Sapper makes these files available as
__assets__ so that you can cache them (though you can choose not to, for example if you don't want to cache very large files).
This is the heart of your Sapper app. There are two kinds of routes — pages, and server routes.
Pages are Svelte components written in
Server routes are modules written in
.js files, that export functions corresponding to HTTP methods. Each function receives Express
response objects as arguments, plus a
next function. This is useful for creating a JSON API, for example.
There are three simple rules for naming the files that define your routes:
- A file called
routes/about.htmlcorresponds to the
/aboutroute. A file called
routes/blog/[slug].htmlcorresponds to the
/blog/:slugroute, in which case
params.slugis available to the route
- The file
routes/index.js) corresponds to the root of your app.
routes/about/index.htmlis treated the same as
- Files and directories with a leading underscore do not create routes. This allows you to colocate helper modules and components with the routes that depend on them — for example you could have a file called
routes/_helpers/datetime.jsand it would not create a
This directory should contain the following files at a minimum:
- 2xx.html — a template for the page to serve for valid requests
- 4xx.html — a template for 4xx-range errors (such as 404 Not Found)
- 5xx.html — a template for 5xx-range errors (such as 500 Internal Server Error)
- main.js — this module initialises Sapper
- service-worker.js — your app's service worker
Inside the HTML templates, Sapper will inject various values as indicated by
__dev__ with the appropriate value.
In lieu of documentation (bear with us), consult the files to see what variables are available and how they're used.
Sapper uses webpack to provide code-splitting, dynamic imports and hot module reloading, as well as compiling your Svelte components. As long as you don't do anything daft, you can edit the configuration files to add whatever loaders and plugins you'd like.
Production mode and deployment
To start a production version of your app, run
npm run build && npm start. This will disable hot module replacement, and activate the appropriate webpack plugins.
You can deploy your application to any environment that supports Node 8 or above. As an example, to deploy to Now, run these commands:
npm install -g now now
Bugs and feedback
Sapper is in early development, and may have the odd rough edge here and there. Please be vocal over on the Sapper issue tracker.