Electron webPreferences preload script, how and where does it run?

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I have been reading through the electron security documentation. https://electronjs.org/docs/tutorial/security trying to understand how I should write my code securely.

From my understanding, I should use the webPreferences and preload script to access features that will access the file system.

I want to have a button that opens a file picker.

I have tried using the preload script but as far as I can tell the script never loads or runs. Can someone explain to me how the preload script works? Where does it load or where can I look in the chrome dev tools to check it has loaded? When does it run, before the page loads or after? Can I still reference funtions in the script from the html file?

const mainWindow = new BrowserWindow({
{width: 800, height: 600},
  webPreferences: {
    nodeIntegration: false,
    preload: `file://${__dirname}/index.js`
  }
});

mainWindow.loadURL(`file://${__dirname}/index.html`);

index.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>Electron Hello World!</title>
  </head>
  <body>
    <h1>Electron Hello World!</h1>
    We are using node <script>document.write(process.versions.node)</script>,
    Chromium <script>document.write(process.versions.chrome)</script>,
    and Electron <script>document.write(process.versions.electron)</script>.
    <br/>
    <button id="openFile" onclick="openFile();">Open</button>
    <br />
    <textarea id="editor" style="width: 400px; height: 300px;"></textarea>
  </body>
</html>

index.ts

{
    console.log('preloaded');
const electron = require('electron').remote;
const dialog = electron.dialog;
const fs = require('fs');
function openFile () {
    dialog.showOpenDialog({filters: [{ name: 'text', extensions: ['txt'] }]}, function (fileNames) {
        if (fileNames === undefined) 
        {
            return;
        }
        var fileName = fileNames[0];
        fs.readFile(fileName, 'utf-8', function (err, data) {
            document.getElementById("editor").innerText = data;
        });
    }); 
} 
}

This code doesn't work. The versions number from the index.html don't display but causes errors in the console. The console.log doesn't run and the button event doesn't work.

0 Answers
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