Input focus not working in electron properly

So far I build a simple Electron application. My problem is the input.focus() is not working on displaying an alert box. I tried to solve the problem, and I came up with a solution: when I minimize and maximize the window, the input.focus() is working well. So when I try to show an alert box, the input.focus() isn't working, except minimize and maximizing. I try to open the code in Chrome, and all functionalities are working very well, so the problem is in the Electron renderer.

Before minimizing and maximizing the window

After minimizing and maximizing the window

My Electron renderer

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

const createWindow = () => {
  const win = new BrowserWindow({
    width: 780,
    height: 600,
    minWidth: 780,
    minHeight: 600,
    icon: path.join(__dirname, "assets/favicon.ico"),
    webPreferences: {},
  });
  win.maximize();
  // win.removeMenu();
  win.loadFile("index.html");
};
app.whenReady().then(() => {
  createWindow();
  app.on("activate", () => {
    if (BrowserWindow.getAllWindows().length === 0)
      createWindow();
  });
});
app.on("window-all-closed", () => {
  if (process.platform !== "darwin")
    app.quit();
});