SO - chaining onloads

http://stackoverflow.com/q/8456733/1011582

HTML

<div id="test"></div>

JavaScript

// previous onload function - defined in another script for example
window.onload = function() {
  document.getElementById("test").innerHTML = "hello";
};

// we will add another function to onload
window.onload = (function() {
  // previous onload function
  var oldonload = window.onload;

  // return new onload function ...
  return function() {
    // .. that will call previous onload
    oldonload();
    // and add something extra
    document.getElementById("test").innerHTML += " world!";
  };
})();