Run a Node.js® Express Server on your Raspberry Pi®

_rpi_nodejs_express_server.md

JavaScript file for running a Node.js® Express server on the Rasbperry Pi®

This gist contains the server code code described in the article Run a Node.js® Express Server on your Raspberry Pi®.

main.js

/*
 * Copyright (c) 2020 - 2022 Persanix LLC. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// Built-in libraries
const fs = require("fs");
const os = require("os");

// Third-party libraries
const express = require("express");


const homeDirectory = os.homedir();

const app = express();

// Respond to GET requests to the route "/files" with a JSON file list or an error
// Note: app.get() corresponds to the HTTP verb GET, similarly app.post() corresponds to POST
app.get("/files", (request, response) => {

    // fs.readdir() is an asynchronous function takes a callback (a function to invoke when the operation is complete)
    fs.readdir(homeDirectory, (error, files) => {

        // Something weird happened, respond with the error message
        // Note: NEVER respond with a stacktrace in a production application. Log the error and move on.
        //       Users seeing a stacktrace is a security vulnerability at worst and poor UX at best
        if (error) {
            return response.status(500).send(error.message);
        }

        // There must not be an error, respond with the file list as JSON
        response.json(files);

    });

});

// Start the server on port 5000 and call console.log() when the server is started (another callback function)
app.listen(5000, () => console.log("Server is up!"));