execute function after complete page load

You're best bet as far as I know is to use

window.addEventListener('load', function() {
    console.log('All assets loaded')
});

The #1 answer of using the DOMContentLoaded event is a step backwards since the DOM will load before all assets load.

Other answers recommend setTimeout which I would strongly oppose since it is completely subjective to the client's device performance and network connection speed. If someone is on a slow network and/or has a slow cpu, a page could take several to dozens of seconds to load, thus you could not predict how much time setTimeout will need.

As for readystatechange, it fires whenever readyState changes which according to MDN will still be before the load event.

Complete

The state indicates that the load event is about to fire.

you can try like this without using jquery

window.addEventListener("load", afterLoaded,false);
function afterLoaded(){
alert("after load")
}

Alternatively you can try below.

$(window).bind("load", function() { 
// code here });

This works in all the case. This will trigger only when the entire page is loaded.

I tend to use the following pattern to check for the document to complete loading. The function returns a Promise (if you need to support IE, include the polyfill) that resolves once the document completes loading. It uses setInterval underneath because a similar implementation with setTimeout could result in a very deep stack.

function getDocReadyPromise()
{
  function promiseDocReady(resolve)
  {
    function checkDocReady()
    {
      if (document.readyState === "complete")
      {
        clearInterval(intervalDocReady);
        resolve();
      }
    }
    var intervalDocReady = setInterval(checkDocReady, 10);
  }
  return new Promise(promiseDocReady);
}

Of course, if you don't have to support IE:

const getDocReadyPromise = () =>
{
  const promiseDocReady = (resolve) =>
  {
    const checkDocReady = () =>
      ((document.readyState === "complete") && (clearInterval(intervalDocReady) || resolve()));
    let intervalDocReady = setInterval(checkDocReady, 10);
  }
  return new Promise(promiseDocReady);
}

With that function, you can do the following:

getDocReadyPromise().then(whatIveBeenWaitingToDo);

call a function after complete page load set time out

setTimeout(function() {
   var val = $('.GridStyle tr:nth-child(2) td:nth-child(4)').text();
 for(var i, j = 0; i = ddl2.options[j]; j++) {
  if(i.text == val) {      
   ddl2.selectedIndex = i.index;
   break;
  }
 } 
}, 1000);

Put your script after the completion of body tag...it works...