Electron function to read a local file

I have an electron project when I need to get electron to read a local file.

Right now what I have is this, where it loads and displays the contents of a html file.

I just need it to read a file and store it on a variable for now.

Here is my current main.js:

const {app, BrowserWindow } = require('electron');
const path = require('path');
const url = require('url');

let mainWindow;

function createWindow () {
  mainWindow = new BrowserWindow({
    width: 1300,
    height: 1000,
    minWidth: 600,
    minHeight: 400,
    title: 'Test App'
  })


  mainWindow.loadURL(url.format({
    pathname: path.join(__dirname, 'index.html'),
    protocol: 'file:',
    slashes: true
  }))


  mainWindow.on('closed', () => {
    mainWindow = null;
  })
}

app.on('ready', createWindow);

app.on('window-all-closed', () => {

  if (process.platform !== 'darwin') {
    app.quit();
  }

});

app.on('activate', () => {
  if (mainWindow === null) {
    createWindow();
  }

});

How can I do this?

via JakeBrown777