Autofill a set of fields (in a gravity form, in this case) based on a checkbox being checked.

gformscopyaddress.js

jQuery(document).ready(function($) {
    $('input#choice_13_1').click(function() {
		if($(this).is(':checked')) {
			$('#input_2_12_1').val($('#input_2_2_1').val());
			$('#input_2_12_2').val($('#input_2_2_2').val());
			$('#input_2_12_3').val($('#input_2_2_3').val());
			$('#input_2_12_4').val($('#input_2_2_4').val());
			$('#input_2_12_5').val($('#input_2_2_5').val());
		};
    });
});

An alternative suggestion for you to consider (untested):

/**
 * Copy values from one field to another if a checkbox is checked.
 * 
 * This function can be re-used - it should be bound to a checkbox element,
 * and passed an object of paired data - { sourceID: destinationID }.
 */
function gmj_copy_fields_if_checked(event) {
    'use strict';

    // Check if checkbox is checked - if not, abort
    if ( ! jQuery(event.target).is(':checked')) {
        return;
    }

    // Loop though fields and assign values
    jQuery.each(event.data, function (key, value) {
        jQuery('#' + key).val(jQuery('#' + value).val());
    });

    // That's it! All we needed to know was the checkbox and the field data, and
    // that's passed through from the element(s) we're bound to, and the data
    // that was sent through at the same time.

}

jQuery(function ($) {
    'use strict';

    // Make an object of data pairs - this could be filtered, made global,
    // pulled out into a wider scope, passed in from PHP via localize script,
    // whatever - we're disassociating our data from the the process we want to
    // run it through to allow code re-use.
    var fields = {
        'input_2_12_1' : 'input_2_2_1',
        'input_2_12_2' : 'input_2_2_2',
        'input_2_12_3' : 'input_2_2_3',
        'input_2_12_4' : 'input_2_2_4',
        'input_2_12_5' : 'input_2_2_5'
    };

    // Bind namespaced event to handler, and pass through fields data.
    // Using namespaces allows us or someone else to be picky about unbinding
    // a handler from a particular event.
    $('#choice_13_1').on('click.gmj', fields, gmj_copy_fields_if_checked);

    // You could have another variable object similar to fields, and you could
    //bind that to some other checkbox, but still use the same function e.g.
    // var = fields2 = { ... }
    // $('#choice_18_2').on('click.gmj', fields2, gmj_copy_fields_if_checked);

});

hi, tnorthcutt & Gary Jones, Thanks for this awesome tweak. Basically i am looking for this code since long time. But the problem praised here is- how to implement this code in my form? Should i copy the code to my theme's function.php file? or some other way?
Please provide the information to use the code.

Has anyone got this working?

Works well here. Thanks a lot.

For anyone still wondering, this needs to go in a javascript file that gets enqueued in functions.php, as here, and should be placed in document.ready(). Another way to do it more generally is the following:

function bindGformHandlers() {
    //bind the click function
    $(document).on('click', '.fill-check input', function() {
        if($(this).is(':checked')) {

            //put in the selectors we fill from
            var fill_from = $('.fill-from, .fill-from .name_last, .fill-from .name_first');
            fill_from.each(function() {

                //get the label
                label = $(this).find('label').text();
                //get the value
                value = $(this).find('input').val();

                //attempt to fill the new field with the value
                to_fill = $('.to-fill label:contains("' + label + '")').siblings().find('input').val(value);
                if(to_fill.length < 1) {
                    //this is so name fields will work
                    to_fill = $('.to-fill label:contains("' + label + '")').siblings('input').val(value);
                }   

            }); 
        }   
    }); 
}

Then all you need to do is create a checkbox with the CSS class "fill-check," give the fields you want to fill from the class "fill-from," and give the fields you want to fill into the class "to-fill" (classes can be added under the "appearance" tab on forms). As long as the labels for the fields are the same, it should work.