...

This rule will automatically fire whenever the user checks or unchecks B and will enable/disable the question in Q. Again, you could use any legal JavaScript expression to compute the enabled property of Q as long as it evaluates to a boolean true or false value. In this example, you would typically set the checkbox B to be initially unchecked and the control Q to be initially disabled.

...

/*member description productId resultSet */
var x;
 
if (form.load) { 
eval('x=' + http.get('http://localhost:8082/database/products'));   
 
    var opts1 = []; 
    var opts2 = []; 
 
    for (var i=0; i < x.resultSet.length; i++) { 
        if (x.resultSet[i]) { 
            opts1[i] = x.resultSet[i].description; 
            opts2[i] = x.resultSet[i].productId; 
    } 
} 
 
 
Products.options = opts1; 
PID.options = opts2; 
Products.value = opts1[0]; // default to 1st product option 
PID.value = opts2[0]; 
}

Finding a Selected Options Index

The 2nd rule Select Product ID keeps the hidden PID dropdown syncronized with the visible Products dropdown.

...

/*member ids products */
var x;
 
if (S.value.length > 0) {
    eval('x=' + http.get('http://localhost:8182/products/?category=' + S.value)); 
    P.options = x.products; 
    ID.options = x.ids; 
}

...

Synchronized Selects

The Product Search example above is often used in conjunction with a hidden select control. Imagine that your database table contains a list of products. Each product has product description also a unique product ID. The user needs to select a product from a dropdown on your form. You want to populate the dropdown with the product descriptions. The users do not need to see or know the product IDs but you need to use the ID as the key into the database for other selects. To do this add another hidden dropdown to the form and populate it with the IDs. This example has a visible dropdown name Products and an invisible dropdown named PID. See the rule above that populates these dropdowns dynamically from the database.

...