Electron: How to display confirmation dialog on beforeunload?

Never mind. I figured it out.

For future reference, here's an example:

window.onbeforeunload = function(e) {
    var remote = require('remote');
    var dialog = remote.require('dialog');
    var choice = dialog.showMessageBox(
            remote.getCurrentWindow(),
            {
                type: 'question',
                buttons: ['Yes', 'No'],
                title: 'Confirm',
                message: 'Are you sure you want to quit?'
            });

    return choice === 0;
};

hi(:
the solution stated above doesn't work for me.
because it still take the "onbeforeunload" of the browser...
any idea?

@shneorasa I know it's been a few months since you asked (and you've probably found a solution by now), but for those looking for a solution in the future, here's a better way in handling this issue as opposed to using window.onbeforeload.

The beforeunload event getting overwritten can potentially mess up future dialogs, breaking your app. Instead, you can store a simple boolean inside your app like I have done:

// Inside main/index.js
import { app, BrowserWindow, dialog } from 'electron'
app.showExitPrompt = true

With that, you can interrupt the close event of your BrowserWindow as follows:

// Inside main/index.js, where BrowserWindow is initialized
mainWindow.on('close', (e) => {
    if (app.showExitPrompt) {
        e.preventDefault() // Prevents the window from closing 
        dialog.showMessageBox({
            type: 'question',
            buttons: ['Yes', 'No'],
            title: 'Confirm',
            message: 'Unsaved data will be lost. Are you sure you want to quit?'
        }, function (response) {
            if (response === 0) { // Runs the following if 'Yes' is clicked
                app.showExitPrompt = false
                mainWindow.close()
            }
        })
    }
})

I have implemented this solution into an Electron app using Vue.js, and showing/hiding the dialog is as simple as importing app:

const { app } = require('electron').remote

and overwriting the stored boolean value:

app.showExitPrompt = true