<input onchange="alert('value changed!');" />

document.getElementById("my_text_input").onchange = function(){
    alert("value changed!");
}

(function(){
    var changed = false;

    document.getElementById("my_text_input").onchange = function(){
        changed = true;
    }
    document.getElementById("my_text_input").onblur = function(){
        if (!changed) {
            //Your logic here
        }
        changed = false; //set it back to false for next loss of focus
    }
})();