Add an onchange event listener to an html input field

Ummm, attach an event handler for the 'change' event?

pure JS

document.getElementById('element_id').onchange = function() {
  // your logic
};

// or

document.getElementById('element_id').addEventListener(
  'change',
  callbackFunction,
  false
);

jQuery

$('#element_id').change(function() {
  // your logic
});

Note

Note, that change event on the text field will be fired after the blur event. It's possible that your looking for keypress event's or something like that.

document.getElementById('cbid.wizard.1._latitude').onchange = function(){
   //do something
}

GlobalEventHandlers.onchange docs

or

document.getElementById('cbid.wizard.1._latitude').addEventListener("change", function(){
    //do something
});

EventTarget.addEventListener docs

use addEventListener in your window.onload

    window.onload=function(){    
document.getElementById('cbid.wizard.1._latitude').addEventListener("change", function(){
            //do something
        });
    };

addEventListener