WooCommerce Checkout add default value to Billing fields if custom checkbox checked - wordpress

Question

I've already created a custom checkbox field in the checkout page with a name of billng_anonymouse, now I want when a customer checks this checkbox it should add a default value to billing_first_name and billing_last_name.
currently, I'm using this function to add a default value for billing fields
function zk_set_checkout_field_input_value_default($fields) {
$fields['billing']['billing_first_name']['default'] = 'First';
$fields['billing']['billing_last_name']['default'] = 'Last';
return $fields;
}
add_filter( 'woocommerce_checkout_fields', 'zk_set_checkout_field_input_value_default' );
but the problem is the default values are always there, how to show them using an IF function only if the checkbox is checked.

Answer 1

You can use custom_attributes in woocommerce_checkout_fields so you have a value stored in attribute to use on checkbox check and uncheck. try the below code.
function zk_set_checkout_field_input_value_default($fields) {
$fields['billing']['billing_first_name']['custom_attributes'] = array( 'data-default' => 'First' );
$fields['billing']['billing_last_name']['custom_attributes'] = array('data-default'=>'Last' );
return $fields;
}
add_filter( 'woocommerce_checkout_fields', 'zk_set_checkout_field_input_value_default' );
function add_custom_checkout_field( $checkout ) {
$current_user = wp_get_current_user();
$billng_anonymouse = $current_user->billng_anonymouse;
woocommerce_form_field( 'billng_anonymouse', array(
'type' => 'checkbox',
'class' => array( 'form-row-wide' ),
'label' => 'Billng anonymouse'
), $checkout->get_value( 'billng_anonymouse' ) );
}
add_action( 'woocommerce_before_checkout_billing_form', 'add_custom_checkout_field' );
function add_custom_js(){
?>
<script type="text/javascript">
(function($){
$(document).on('change', '#billng_anonymouse', function(event) {
if( $(this).is(':checked') ){
$('#billing_first_name').val($('#billing_first_name').data('default'));
$('#billing_last_name').val($('#billing_last_name').data('default'));
}else{
$('#billing_first_name').val('');
$('#billing_last_name').val('');
}
});
})(jQuery);
</script>
<?php
}
add_action( 'woocommerce_after_checkout_form', 'add_custom_js', 10, 1 );
Tested and works.