Question

I have a form that allows the user to enter a weight, in either pounds or kilograms.

I’d like to store all of the data in kilograms, and using jQuery, would like the form to convert the weight_value to kilograms and change the weight_units option to “kg”.

1 pound = 0.45359237 kilograms

The function should round the weight_value to the nearest kilogram (no decimals).

Any help you could provide would be appreciated!

<label> Weight:</label>
<input type="text" id="weight_value" />
<select id="weight_unit" />
   <option value="lbs">lbs</option>
   <option value="kg">kg</option>
</select>

Answer 1

Here is a try:

var kg = 0.45359237

$(document).ready(function() {
    $("#weight_unit").change(function() {
        if ($(this).val() == "kg") {
            $("#weight_value").val(Math.round( $("#weight_value").val()*kg))
        } else {
            $("#weight_value").val(Math.round( $("#weight_value").val()/kg))
        }
    });
});

See it live on: http://jsfiddle.net/zeByX/

[EDIT] With the Math.floor(), you can get some weird results by switching from kg to pounds (try with 12 pounds and switch).