Using Different Servers with Svelte

Svelte by default uses the Node.JS http module as it's router. Here we will talk about using Express or Polka as middleware to implement API routes.


We won't go over installing Express or Polka here.

Using adapter-node

Using Express

After building the application for node, Svelte will output two files, handler.js and index.js. The handler.js file will be the file you pass into Express as middleware.

Next, make a new file and paste the following code into it. This import the handler.js file into an express server and adds a /healthcheck route then starts the server on port 3000. If you built the application in a different directory make sure to change the ./build/handler.js route.

 1import { handler } from "./build/handler.js";
 2import express from "express";
 4const app = express();
 6// add a route that lives separately from the SvelteKit app
 7app.get("/healthcheck", (req, res) => {
 8  res.end("ok");
11// let SvelteKit handle everything else, including serving prerendered pages and static assets
14app.listen(3000, () => {
15  console.log("listening on port 3000");

Using Polka

Polka and Express have very simular APIs, which makes using them interchangeably very easy. To use polka simply replace the import statement for express with polka and everything will work.