CIS 119 Nested selection

The code

The HTML:

<p><button id="cow">Cow</button></p>
<p><button id="pig">Pig</button></p>
<p><button id="duck">Duck</button></p>

The JavaScript:

function showSound() {
    var animal = this.id;
    if (animal === 'cow') {
        alert('Mooo');
    } else {
        if (animal === 'pig') {
            alert('Oink');
        } else {  // must be a duck
            alert('Quack');
        }
    }
}

function init() {
    document.getElementById('cow').onclick = showSound;
    document.getElementById('pig').onclick = showSound;
    document.getElementById('duck').onclick = showSound;
}

window.onload = init;