JSFiddle - React, Tailwind, and code Playground

HTML

<form>
<input type="button" value="Click me!" onclick="window.displaymessage()" />
</form>

<p>By pressing the button above, a function will be called. The function will alert a message.</p>

JavaScript

window.displaymessage= function ()
{    
  var cities = ["London", "San Francisco", "Tokyo", "Barcelona", "Sydney"]
  var sortedCities = cities.sort()
  
  indexOfLondon = sortedCities.indexOf("London")+1
  alert("London is city number " + indexOfLondon + " in the list")
    
  alert(sortedCities)
   
    
}