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());
		};
    });
});

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.