Edit in JSFiddle

function add(a, b, c) {
    return a + b + c;
}

$(document).ready(function() {

    var resultDiv = document.getElementById('results'),
        result = add(1, 2, 3),
        result2Arguments = add(1, 2),
        result4Arguments = add(1, 2, 3, 4);

    resultDiv.innerHTML += result + "<br />";
    resultDiv.innerHTML += result2Arguments + "<br />";
    resultDiv.innerHTML += result4Arguments + "<br />";
});

<p>Results:</p>

<div id='results'>
</div>