require module inside preload script in electron

Question

I'm building an app with electron react and MySQL, I'm stuck in preload script where i want to make my db instance available in render-er process, i got the following error Error: module not found: ./config/db in console. this happening when i try to require a module inside preload script.

const { app, BrowserWindow } = require("electron");
const path = require("path");
const isDev = require("electron-is-dev");
const dotenv = require("dotenv");

//load .env
dotenv.config();

function createWindow() {
  // Create the browser window.
  const mainWindow = new BrowserWindow({
    title: "Electron",
    minWidth: 800,
    minHeight: 600,
    webPreferences: {
      preload: path.join(__dirname, "preload.js"),
      devTools: isDev,
    },
  });

  //get url dependig on envirement (dev/prod)
  const url = isDev
    ? `http://localhost:${process.env.PORT}/`
    : `file://${path.join(__dirname, "../../dist/react/index.html")}`;

  // load the url
  mainWindow.loadURL(url);

  // Open the DevTools.
  isDev && mainWindow.webContents.openDevTools();
}

// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.
app.whenReady().then(() => {
  createWindow();

  app.on("activate", function () {
    // On macOS it's common to re-create a window in the app when the
    // dock icon is clicked and there are no other windows open.
    if (BrowserWindow.getAllWindows().length === 0) createWindow();
  });
});

// Quit when all windows are closed, except on macOS. There, it's common
// for applications and their menu bar to stay active until the user quits
// explicitly with Cmd + Q.
app.on("window-all-closed", function () {
  if (process.platform !== "darwin") app.quit();
});

// In this file you can include the rest of your app's specific main process
// code. You can also put them in separate files and require them here.

require("./handlers");

preload

const { contextBridge, ipcRenderer } = require("electron");
const { db } = require("./config/db");

contextBridge.exposeInMainWorld("mainApi", {
  db,
});

Answer 1

Since Electron v20.0.0, the sandbox parameter defaults to true (according to the list of Breaking Changes )

One of the side effects of the sandbox attribute is that it can only require a few things :

A require function similar to Node's require module is exposed, but can only import a subset of Electron and Node's built-in modules:

 electron (only renderer process modules) events timers url

To disable sandboxing, just add sandbox: false to your webPreferences on window creation:

  // ...

  // Create the browser window.
  const mainWindow = new BrowserWindow({
    title: "Electron",
    minWidth: 800,
    minHeight: 600,
    webPreferences: {
      preload: path.join(__dirname, "preload.js"),
      devTools: isDev,
      sandbox: false, // fixes require() in preloader
    },
  });

  // ...