Question

I’m trying to get the javascript below to automatically update the input field (centimeters) below when a user select there height and inches. It should auto calculate the centimeters, and its not working.

<script type=​"text/​javascript">​
updateHeights:function(type){
    if(type=='english'){
        var feet=parseInt($F('feet'));
        var inches=parseInt($F('inches'));
        var cm=((feet*12+inches)*2.54).round();
        $('centimeters').value=(feet?cm:'');
        } 
        else 
        {
        var cm=parseInt($F('centimeters'))||183;
    if(cm>241||cm<91)cm=183;
        var inches_total=(cm*0.3937).round();
        var feet=(inches_total/12).floor();
        var inches=inches_total%12;
        $('feet').value=feet;
        $('inches').value=inches;
        $('centimeters').value=cm;
    }
}
</script>

<label>Height:</label>
<select id="feet" name="add[feet]" onchange="Profile.updateHeights('english')">
    <option value="">—</option>
    <option value="7">7</option>
    <option value="6">6</option>
    <option value="5">5</option>
    <option value="4">4</option>
    <option value="3">3</option>
</select>ft.&nbsp;&nbsp;
<select id="inches" name="add[inch]" onchange="Profile.updateHeights('english')">
    <option value="0">0</option>
    <option value="1">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
    <option value="4">4</option>
    <option value="5">5</option>
    <option value="6">6</option>
    <option value="7">7</option>
    <option value="8">8</option>
    <option value="9">9</option>
    <option value="10">10</option>
    <option value="11">11</option>
</select>in. or&nbsp;
<input id="centimeters" type="text" name="centimeters" maxlength="3" value="178" onchange="Profile.updateHeights('metric')" style="width: 30px;" />
&nbsp;centimeters

Answer 1

Assuming that this is just an excerpt from your entire code, Profile is a legitimate class name, and $F is defined somewhere, you’re missing a few things.

First off, you’re selecting by ID, so you need to include the # sign in your selectors.
Second, you’re trying to parse an object as an integer. You need to use parseInt($("#feet").val()) to select the value contained in the input. Likewise, to set a value, you’re going to want to use $("#centimeters").val(cm);