wp_prepare_themes_for_js( array $themes = null )

function wp_prepare_themes_for_js( $themes = null ) {
	$current_theme = get_stylesheet();

	/**
	 * Filters theme data before it is prepared for JavaScript.
	 *
	 * Passing a non-empty array will result in wp_prepare_themes_for_js() returning
	 * early with that value instead.
	 *
	 * @since WP-4.2.0
	 *
	 * @param array      $prepared_themes An associative array of theme data. Default empty array.
	 * @param null|array $themes          An array of WP_Theme objects to prepare, if any.
	 * @param string     $current_theme   The current theme slug.
	 */
	$prepared_themes = (array) apply_filters( 'pre_prepare_themes_for_js', array(), $themes, $current_theme );

	if ( ! empty( $prepared_themes ) ) {
		return $prepared_themes;
	}

	// Make sure the current theme is listed first.
	$prepared_themes[ $current_theme ] = array();

	if ( null === $themes ) {
		$themes = wp_get_themes( array( 'allowed' => true ) );
		if ( ! isset( $themes[ $current_theme ] ) ) {
			$themes[ $current_theme ] = wp_get_theme();
		}
	}

	$updates = array();
	if ( current_user_can( 'update_themes' ) ) {
		$updates_transient = get_site_transient( 'update_themes' );
		if ( isset( $updates_transient->response ) ) {
			$updates = $updates_transient->response;
		}
	}

	WP_Theme::sort_by_name( $themes );

	$parents = array();

	foreach ( $themes as $theme ) {
		$slug = $theme->get_stylesheet();
		$encoded_slug = urlencode( $slug );

		$parent = false;
		if ( $theme->parent() ) {
			$parent = $theme->parent();
			$parents[ $slug ] = $parent->get_stylesheet();
			$parent = $parent->display( 'Name' );
		}

		$customize_action = null;
		if ( current_user_can( 'edit_theme_options' ) && current_user_can( 'customize' ) ) {
			$customize_action = esc_url( add_query_arg(
				array(
					'return' => urlencode( esc_url_raw( remove_query_arg( wp_removable_query_args(), wp_unslash( $_SERVER['REQUEST_URI'] ) ) ) ),
				),
				wp_customize_url( $slug )
			) );
		}

		$prepared_themes[ $slug ] = array(
			'id'           => $slug,
			'name'         => $theme->display( 'Name' ),
			'screenshot'   => array( $theme->get_screenshot() ), // @todo multiple
			'description'  => $theme->display( 'Description' ),
			'author'       => $theme->display( 'Author', false, true ),
			'authorAndUri' => $theme->display( 'Author' ),
			'version'      => $theme->display( 'Version' ),
			'tags'         => $theme->display( 'Tags' ),
			'parent'       => $parent,
			'active'       => $slug === $current_theme,
			'hasUpdate'    => isset( $updates[ $slug ] ),
			'hasPackage'   => isset( $updates[ $slug ] ) && ! empty( $updates[ $slug ][ 'package' ] ),
			'update'       => get_theme_update_available( $theme ),
			'actions'      => array(
				'activate' => current_user_can( 'switch_themes' ) ? wp_nonce_url( admin_url( 'themes.php?action=activate&stylesheet=' . $encoded_slug ), 'switch-theme_' . $slug ) : null,
				'customize' => $customize_action,
				'delete'   => current_user_can( 'delete_themes' ) ? wp_nonce_url( admin_url( 'themes.php?action=delete&stylesheet=' . $encoded_slug ), 'delete-theme_' . $slug ) : null,
			),
		);
	}

	// Remove 'delete' action if theme has an active child
	if ( ! empty( $parents ) && array_key_exists( $current_theme, $parents ) ) {
		unset( $prepared_themes[ $parents[ $current_theme ] ]['actions']['delete'] );
	}

	// Indicate a preferred ClassicPress child theme for the WP parent themes
	$wp_theme_slugs = array( 'twentyfifteen', 'twentysixteen', 'twentyseventeen' );
	foreach ( $wp_theme_slugs as $slug ) {
		if (
			isset( $prepared_themes[ $slug ] ) &&
			isset( $prepared_themes[ "classicpress-$slug" ] )
		) {
			$prepared_themes[ $slug ]['preferredChildName'] =
				$prepared_themes[ "classicpress-$slug" ]['name'];
		}
	}

	/**
	 * Filters the themes prepared for JavaScript, for themes.php.
	 *
	 * Could be useful for changing the order, which is by name by default.
	 *
	 * @since WP-3.8.0
	 *
	 * @param array $prepared_themes Array of themes.
	 */
	$prepared_themes = apply_filters( 'wp_prepare_themes_for_js', $prepared_themes );
	$prepared_themes = array_values( $prepared_themes );
	return array_filter( $prepared_themes );
}