Form field "showon" with multiple fields

Question

I have 3 fields defined in my XML file like so:

<field name="field1" type="radio" label="Field 1" class="btn-group" default="1">
    <option value="1">JYES</option>
    <option value="0">JNO</option>
</field>

<field name="field2" type="radio" label="Field 2" class="btn-group" default="1">
    <option value="1">JYES</option>
    <option value="0">JNO</option>
</field>

<field name="field3" type="radio" label="Field 3" class="btn-group" default="1">
    <option value="1">JYES</option>
    <option value="0">JNO</option>
</field>

Now what I'd like to do is only show field3 if field1 and field2 are set to 1.

Answer 1

You can chain the attribute values of showon, using [AND], like so:

showon="field1:1[AND]field2:1"

Adding more fields to the chain is also allowed.

On a side note, you can use an [OR] clause in the chain too, adding more complexity, for example:

showon="field1:1[AND]field2:1[OR]fieldX:1"

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Update for Joomla 3.7:

As of Joomla 3.7, you will be able to to use the ! operator (not equal to):

showon="field1!:1"

This means, if field1 does not equal 1