Script allows you to test freeze in web application

app-freeze.js

function freezeApp(duration) {
  var now = new Date().getTime();
  var endTime = now + duration;
  console.log('start freeze time', new Date().toISOString(), 'window is focused:', document.hasFocus());
  while(new Date().getTime() < endTime) document.querySelector('this.is > [very] > *[heavy] > .css[selector]');
  console.log('end freeze time', new Date().toISOString(), 'window is focused:', document.hasFocus());
}

/**
 * Freeze app for 5000ms with 2000ms delay
 */
setTimeout(() => freezeApp(5000), 2000)