async window.open()

index.js

window.onclick = () => {
  // You MUST create the window on the same event
  // tick/stack as the user-initiated event (e.g. click callback)
  const googleWindow = window.open();

  // Do your async work
  fakeAjax(response => {
    // Change the URL of the window you created once you
    // know what the full URL is!
    googleWindow.location.replace(`https://google.com?q=${response}`);
  });
};

function fakeAjax(callback) {
  setTimeout(() => {
    callback('example');
  }, 1000);
}