Registering Event Handler

Setting Event Handler Properties

    window.onload = function() {
    // Look up a <form> element
    var elt = document.getElementById("shipping_address");
    // Register an event handler function that will be invoked right // before the form is submitted.
    elt.onsubmit = function() { return validate(this); }
    }

Setting Event Handler Attributes

    <button onclick="alert('Thank you');">Click Here</button>

addEventListener()

    <button id="mybutton">Click me</button>
    <script>
    var b = document.getElementById("mybutton");
    b.onclick = function() { alert("Thanks for clicking me!"); }; 
    b.addEventListener("click", function() {
    alert("Thanks again!"); }, false); 
    </script>

attachEvent()

The attachEvent() and detachEvent() methods work like addEventListener() and removeEventListener()