Ran into this recently and it seems that in the traditional "widgets.php" interface any javascript initialization should be run directly for existing widgets (those in the #widgets-right div), and indirectly via the widget-added event for newly added widgets; whereas in the customizer "customize.php" interface all widgets - existing and new - are sent the widget-added event so can just be initialized there. Based on this the following is an extension of the WP_Widget class which makes it easy to add javascript initialization to a widget's form by overriding one function, form_javascript_init():
class WPSE_JS_Widget extends WP_Widget { // For widgets using javascript in form().
var $js_ns = 'wpse'; // Javscript namespace.
var $js_init_func = ''; // Name of javascript init function to call. Initialized in constructor.
var $is_customizer = false; // Whether in customizer or not. Set on 'load-customize.php' action (if any).
public function __construct( $id_base, $name, $widget_options = array(), $control_options = array(), $js_ns = '' ) {
parent::__construct( $id_base, $name, $widget_options, $control_options );
if ( $js_ns ) {
$this->js_ns = $js_ns;
}
$this->js_init_func = $this->js_ns . '.' . $this->id_base . '_init';
add_action( 'load-widgets.php', array( $this, 'load_widgets_php' ) );
add_action( 'load-customize.php', array( $this, 'load_customize_php' ) );
}
// Called on 'load-widgets.php' action added in constructor.
public function load_widgets_php() {
add_action( 'in_widget_form', array( $this, 'form_maybe_call_javascript_init' ) );
add_action( 'admin_print_scripts', array( $this, 'admin_print_scripts' ), PHP_INT_MAX );
}
// Called on 'load-customize.php' action added in constructor.
public function load_customize_php() {
$this->is_customizer = true;
// Don't add 'in_widget_form' action as customizer sends 'widget-added' event to existing widgets too.
add_action( 'admin_print_scripts', array( $this, 'admin_print_scripts' ), PHP_INT_MAX );
}
// Form javascript initialization code here. "widget" and "widget_id" available.
public function form_javascript_init() {
}
// Called on 'in_widget_form' action (ie directly after form()) when in traditional widgets interface.
// Run init directly unless we're newly added.
public function form_maybe_call_javascript_init( $callee_this ) {
if ( $this === $callee_this && '__i__' !== $this->number ) {
?>
<script type="text/javascript">
jQuery(function ($) {
<?php echo $this->js_init_func; ?>(null, $('#widgets-right [id$="<?php echo $this->id; ?>"]'));
});
</script>
<?php
}
}
// Called on 'admin_print_scripts' action added in constructor.
public function admin_print_scripts() {
?>
<script type="text/javascript">
var <?php echo $this->js_ns; ?> = <?php echo $this->js_ns; ?> || {}; // Our namespace.
jQuery(function ($) {
<?php echo $this->js_init_func; ?> = function (e, widget) {
var widget_id = widget.attr('id');
if (widget_id.search(/^widget-[0-9]+_<?php echo $this->id_base; ?>-[0-9]+$/) === -1) { // Check it's our widget.
return;
}
<?php $this->form_javascript_init(); ?>
};
$(document).on('widget-added', <?php echo $this->js_init_func; ?>); // Call init on widget add.
});
</script>
<?php
}
}
An example test widget using this:
class WPSE_Test_Widget extends WPSE_JS_Widget {
var $defaults; // Form defaults. Initialized in constructor.
function __construct() {
parent::__construct( 'wpse_test_widget', __( 'WPSE: Test Widget' ), array( 'description' => __( 'Test init of javascript.' ) ) );
$this->defaults = array(
'one' => false,
'two' => false,
'color' => '#123456',
);
add_action( 'admin_enqueue_scripts', function ( $hook_suffix ) {
if ( ! in_array( $hook_suffix, array( 'widgets.php', 'customize.php' ) ) ) return;
wp_enqueue_script( 'wp-color-picker' ); wp_enqueue_style( 'wp-color-picker' );
} );
}
function widget( $args, $instance ) {
extract( $args );
extract( wp_parse_args( $instance, $this->defaults ) );
echo $before_widget, '<p style="color:', $color, ';">', $two ? 'Two' : ( $one ? 'One' : 'None' ), '</p>', $after_widget;
}
function update( $new_instance, $old_instance ) {
$new_instance['one'] = isset( $new_instance['one'] ) ? 1 : 0;
$new_instance['two'] = isset( $new_instance['two'] ) ? 1 : 0;
return $new_instance;
}
function form( $instance ) {
extract( wp_parse_args( $instance, $this->defaults ) );
?>
<div class="wpse_test">
<p class="one">
<input class="checkbox" type="checkbox" <?php checked( $one ); disabled( $two ); ?> id="<?php echo $this->get_field_id( 'one' ); ?>" name="<?php echo $this->get_field_name( 'one' ); ?>" />
<label for="<?php echo $this->get_field_id( 'one' ); ?>"><?php _e( 'One?' ); ?></label>
</p>
<p class="two">
<input class="checkbox" type="checkbox" <?php checked( $two ); disabled( $one ); ?> id="<?php echo $this->get_field_id( 'two' ); ?>" name="<?php echo $this->get_field_name( 'two' ); ?>" />
<label for="<?php echo $this->get_field_id( 'two' ); ?>"><?php _e( 'Two?' ); ?></label>
</p>
<p class="color">
<input type="text" value="<?php echo htmlspecialchars( $color ); ?>" id="<?php echo $this->get_field_id( 'color' ); ?>" name="<?php echo $this->get_field_name( 'color' ); ?>" />
</p>
</div>
<?php
}
// Form javascript initialization code here. "widget" and "widget_id" available.
function form_javascript_init() {
?>
$('.one input', widget).change(function (event) { $('.two input', widget).prop('disabled', this.checked); });
$('.two input', widget).change(function (event) { $('.one input', widget).prop('disabled', this.checked); });
$('.color input', widget).wpColorPicker({
<?php if ( $this->is_customizer ) ?> change: _.throttle( function () { $(this).trigger('change'); }, 1000, {leading: false} )
});
<?php
}
}
add_action( 'widgets_init', function () {
register_widget( 'WPSE_Test_Widget' );
} );
