Change Variables Depending on Selected Set of Checkbox
<p>I have a set of checkbox which has different values depending on the combination of selected boxes, but the code I made didn't work, I was thinking maybe the location of my &amp;&amp; sign is not in proper position but I don't know where exactly I can put it to run the code.</p>

<p>Here is the html code:</p>

<pre><code>&lt;form role="form" id="checkbox" name="checkbox" onclick="changevalue()"&gt;
    &lt;input type="checkbox" id="f1"&gt;Full Front
    &lt;input type="checkbox" id="b1"&gt;Full Back
    &lt;input type="checkbox" id="f2"&gt;Pocket
&lt;/form&gt;

&lt;input type="number" id="checkboxResult"&gt;
</code></pre>

<p>And here is the script:</p>

<pre><code> &lt;script type="text/javascript"&gt;
    function changevalue(form){
        var chkboxvalue = 0;
            if (document.getElementById('f1').checked) &amp;&amp;
            if (document.getElementById('b1').checked) {
                chkboxvalue = 2.2;
            };

            if (document.getElementById('f2').checked) &amp;&amp;
            if (document.getElementById('b1').checked) {
                chkboxvalue = 1.7;
            };

        document.getElementById('checkboxResult').value = chkboxvalue;
    }
&lt;/script&gt;
</code></pre>