Error document.form is undefined in javascript
<p>I have a code javascript:</p>

<pre><code>&lt;form onsubmit="return false;" action=""&gt;
&lt;input type="radio" name="type" id="type0" value="0" onclick="toggleSet(this)" checked /&gt;type 0
&lt;input type="radio" name="type" id="type1" value="1" onclick="toggleSet(this)" /&gt;Type 1
&lt;/form&gt;
&lt;script&gt;
function toggleSet() {
    for(var i=0; i&lt;document.form.type.length; i++) {
        if(document.form.type[i].checked) {
            var type = document.form.type[i].value;
        }
    }
    alert(type);
}
&lt;/script&gt;
</code></pre>

<p>ouput error: document.form is undefined, how to fix it ?</p>
