javascript - How to prevent default on form submit?

Question

If I do this I can prevent default on form submit just fine:

document.getElementById('my-form').onsubmit(function(e) {
   e.preventDefault();
   // do something
});

But since I am organizing my code in a modular way I am handling events like this:

document.getElementById('my-form').addEventListener('onsubmit', my_func);

var my_func = function() {
   // HOW DO I PREVENT DEFAULT HERE???
   // do something
}

How can I prevent default now?

Answer 1

The same way, actually!

// your function
var my_func = function(event) {
    alert("me and all my relatives are owned by China");
    event.preventDefault();
};

// your form
var form = document.getElementById("panda");

// attach event listener
form.addEventListener("submit", my_func, true);

<form id="panda" method="post">
    <input type="submit" value="The Panda says..."/>
</form>