How to access DOM elements in electron?

I am trying to add functionality to a button in index.html file is as follows: I have a button element in index.html

<button id="auth-button">Authorize</button>

In main.js of the app, I have

require('crash-reporter').start();
console.log("oh yaeh!");
var mainWindow = null;

app.on('window-all-closed', function(){
	if(process.platform != 'darwin'){
		app.quit();
	}
});

app.on('ready',function(){
	mainWindow = new BrowserWindow({width:800, height : 600});
	mainWindow.loadUrl('file://' + __dirname + '/index.html');

    var authButton = document.getElementById("auth-button");
    authButton.addEventListener("click",function(){alert("clicked!");});

	mainWindow.openDevTools();

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

But an error occurs as follows: Uncaught Exception: ReferenceError: document is not defined

Can the DOM objects be accessed while building electron apps? or is there any other alternative way that can give me the required functionality?

DOM can not be accessed in the main process, only in the renderer that it belongs to.

There is an ipc module, available on main process as well as the renderer process that allows the communication between these two via sync/async messages.

You also can use the remote module to call main process API from the renderer, but there's nothing that would allow you to do it the other way around.

If you need to run something in the main process as a response to user action, use the ipc module to invoke the function, then you can return a result to the renderer, also using ipc.

Code updated to reflect actual (v0.37.8) API, as @Wolfgang suggested in comment, see edit history for deprecated API, if you are stuck with older version of Electron.

Example script in index.html:

var ipc = require('electron').ipcRenderer;
var authButton = document.getElementById('auth-button');
authButton.addEventListener('click', function(){
	ipc.once('actionReply', function(event, response){
		processResponse(response);
	})
	ipc.send('invokeAction', 'someData');
});

And in the main process:

var ipc = require('electron').ipcMain;

ipc.on('invokeAction', function(event, data){
	var result = processData(data);
	event.sender.send('actionReply', result);
});

You can use webContents.executeJavaScript(code[, userGesture, callback]) API to execute JavaScript code.

for example:

mainWindow.loadUrl('file://' + __dirname + '/index.html');
mainWindow.webContents.on('did-finish-load', ()=>{
    let code = `var authButton = document.getElementById("auth-button");
            authButton.addEventListener("click",function(){alert("clicked!");});`;
    mainWindow.webContents.executeJavaScript(code);
});

As stated in this tutorial:

> In Electron, we have several ways to communicate between the main process and renderer processes, such as ipcRenderer and ipcMain modules for sending messages, and the remote module for RPC style communication.

So you can follow the example in https://github.com/electron/electron-api-demos. You should have a js file for each html. In that js file, you can use require anytime you want.

Code in renderer.js:

const ipc = require('electron').ipcRenderer

const asyncMsgBtn = document.getElementById('async-msg')

asyncMsgBtn.addEventListener('click', function () {
  ipc.send('asynchronous-message', 'ping')
})

ipc.on('asynchronous-reply', function (event, arg) {
  const message = `Asynchronous message reply: ${arg}`
  document.getElementById('async-reply').innerHTML = message
})

Code in ipc.html:

<script type="text/javascript">
  require('./renderer-process/communication/sync-msg')
  require('./renderer-process/communication/async-msg')
  require('./renderer-process/communication/invisible-msg')
</script>

in my case the window was created by invoking window.open by default electron NodeIntegration is disabled, so you can't access the DOM of the other window. changing the property nativeWindowOpen to true fixed my issue.

// in main.ts
async function createWindow() {
  const win = new BrowserWindow({
    // ....
    webPreferences: {
      nativeWindowOpen: true,
    }
  })

Now i can access the window.document element when i create the window using window.open