Default true.
	 * @return bool|string|void Void if no data exists, extra scripts if `$echo` is true, true otherwise.
	 */
	public function print_extra_script( $handle, $echo = true ) {
		if ( !$output = $this->get_data( $handle, 'data' ) )
			return;

		if ( !$echo )
			return $output;

		echo "<script type='text/javascript'>\n"; // CDATA and type='text/javascript' is not needed for HTML 5
		echo "/* <![CDATA[ */\n";
		echo "$output\n";
		echo "/* ]]> */\n";
		echo "</script>\n";

		return true;
	}

	/**
	 * Processes a script dependency.
	 *
	 * @since 2.6.0
	 * @since 2.8.0 Added the `$group` parameter.
	 *
	 * @see WP_Dependencies::do_item()
	 *
	 * @param string $handle    The script's registered handle.
	 * @param int|false $group  Optional. Group level: (int) level, (false) no groups. Default false.
	 * @return bool True on success, false on failure.
	 */
	public function do_item( $handle, $group = false ) {
		if ( !parent::do_item($handle) )
			return false;

		if ( 0 === $group && $this->groups[$handle] > 0 ) {
			$this->in_footer[] = $handle;
			return false;
		}

		if ( false === $group && in_array($handle, $this->in_footer, true) )
			$this->in_footer = array_diff( $this->in_footer, (array) $handle );

		$obj = $this->registered[$handle];

		if ( null === $obj->ver ) {
			$ver = '';
		} else {
			$ver = $obj->ver ? $obj->ver : $this->default_version;
		}

		if ( isset($this->args[$handle]) )
			$ver = $ver ? $ver . '&amp;' . $this->args[$handle] : $this->args[$handle];

		$src = $obj->src;
		$cond_before = $cond_after = '';
		$conditional = isset( $obj->extra['conditional'] ) ? $obj->extra['conditional'] : '';

		if ( $conditional ) {
			$cond_before = "<!--[if {$conditional}]>\n";
			$cond_after = "<![endif]-->\n";
		}

		$before_handle = $this->print_inline_script( $handle, 'before', false );
		$after_handle = $this->print_inline_script( $handle, 'after', false );

		if ( $before_handle ) {
			$before_handle = sprintf( "<script type='text/javascript'>\n%s\n</script>\n", $before_handle );
		}

		if ( $after_handle ) {
			$after_handle = sprintf( "<script type='text/javascript'>\n%s\n</script>\n", $after_handle );
		}

		if ( $this->do_concat ) {
			/**
			 * Filters the script loader source.
			 *
			 * @since 2.2.0
			 *
			 * @param string $src    Script loader source path.
			 * @param string $handle Script handle.
			 */
			$srce = apply_filters( 'script_loader_src', $src, $handle );

			if ( $this->in_default_dir( $srce ) && ( $before_handle || $after_handle ) ) {
				$this->do_concat = false;

				// Have to print the so-far concatenated scripts right away to maintain the right order.
				_print_scripts();
				$this->reset();
			} elseif ( $this->in_default_dir( $srce ) && ! $conditional ) {
				$this->print_code .= $this->print_extra_script( $handle, false );
				$this->concat .= "$handle,";
				$this->concat_version .= "$handle$ver";
				return true;
			} else {
				$this->ext_handles .= "$handle,";
				$this->ext_version .= "$handle$ver";
			}
		}

		$has_conditional_data = $conditional && $this->get_data( $handle, 'data' );

		if ( $has_conditional_data ) {
			echo $cond_before;
		}

		$this->print_extra_script( $handle );

		if ( $has_conditional_data ) {
			echo $cond_after;
		}

		// A single item may alias a set of items, by having dependencies, but no source.
		if ( ! $obj->src ) {
			return true;
		}

		if ( ! preg_match( '|^(https?:)?//|', $src ) && ! ( $this->content_url && 0 === strpos( $src, $this->content_url ) ) ) {
			$src = $this->base_url . $src;
		}

		if ( ! empty( $ver ) )
			$src = add_query_arg( 'ver', $ver, $src );

		/** This filter is documented in wp-includes/class.wp-scripts.php */
		$src = esc_url( apply_filters( 'script_loader_src', $src, $handle ) );

		if ( ! $src )
			return true;

		$tag = "{$cond_before}{$before_handle}<script type='text/javascript' src='$src'></script>\n{$after_handle}{$cond_after}";

		/**
		 * Filters the HTML script tag of an enqueued script.
		 *
		 * @since 4.1.0
		 *
		 * @param string $tag    The `<script>` tag for the enqueued script.
		 * @param string $handle The script's registered handle.
		 * @param string $src    The script's source URL.
		 */
		$tag = apply_filters( 'script_loader_tag', $tag, $handle, $src );

		if ( $this->do_concat ) {
			$this->print_html .= $tag;
		} else {
			echo $tag;
		}

		return true;
	}

	/**
	 * Adds extra code to a registered script.
	 *
	 * @since 4.5.0
	 *
	 * @param string $handle   Name of the script to add the inline script to. Must be lowercase.
	 * @param string $data     String containing the javascript to be added.
	 * @param string $position Optional. Whether to add the inline script before the handle
	 *                         or after. Default 'after'.
	 * @return bool True on success, false on failure.
	 */
	public function add_inline_script( $handle, $data, $position = 'after' ) {
		if ( ! $data ) {
			return false;
		}

		if ( 'after' !== $position ) {
			$position = 'before';
		}

		$script   = (array) $this->get_data( $handle, $position );
		$script[] = $data;

		return $this->add_data( $handle, $position, $script );
	}

	/**
	 * Prints inline scripts registered for a specific handle.
	 *
	 * @since 4.5.0
	 *
	 * @param string $handle   Name of the script to add the inline script to. Must be lowercase.
	 * @param string $position Optional. Whether to add the inline script before the handle
	 *                         or after. Default 'after'.
	 * @param bool $echo       Optional. Whether to echo the script instead of just returning it.
	 *                         Default true.
	 * @return string|false Script on success, false otherwise.
	 */
	public function print_inline_script( $handle, $position = 'after', $echo = true ) {
		$output = $this->get_data( $handle, $position );

		if ( empty( $output ) ) {
			return false;
		}

		$output = trim( implode( "\n", $output ), "\n" );

		if ( $echo ) {
			printf( "<script type='text/javascript'>\n%s\n</script>\n", $output );
		}

		return $output;
	}

	/**
	 * Localizes a script, only if the script has already been added.
	 *
	 * @since 2.1.0
	 *
	 * @param string $handle
	 * @param string $object_name
	 * @param array $l10n
	 * @return bool
	 */
	public function localize( $handle, $object_name, $l10n ) {
		if ( $handle === 'jquery' )
			$handle = 'jquery-core';

		if ( is_array($l10n) && isset($l10n['l10n_print_after']) ) { // back compat, preserve the code in 'l10n_print_after' if present
			$after = $l10n['l10n_print_after'];
			unset($l10n['l10n_print_after']);
		}

		foreach ( (array) $l10n as $key => $value ) {
			if ( !is_scalar($value) )
				continue;

			$l10n[$key] = html_entity_decode( (string) $value, ENT_QUOTES, 'UTF-8');
		}

		$script = "var $object_name = " . wp_json_encode( $l10n ) . ';';

		if ( !empty($after) )
			$script .= "\n$after;";

		$data = $this->get_data( $handle, 'data' );

		if ( !empty( $data ) )
			$script = "$data\n$script";

		return $this->add_data( $handle, 'data', $script );
	}

	/**
	 * Sets handle group.
	 *
	 * @since 2.8.0
	 *
	 * @see WP_Dependencies::set_group()
	 *
	 * @param string    $handle    Name of the item. Should be unique.
	 * @param bool      $recursion Internal flag that calling function was called recursively.
	 * @param int|false $group     Optional. Group level: (int) level, (false) no groups. Default false.
	 * @return bool Not already in the group or a lower group
	 */
	public function set_group( $handle, $recursion, $group = false ) {
		if ( isset( $this->registered[$handle]->args ) && $this->registered[$handle]->args === 1 )
			$grp = 1;
		else
			$grp = (int) $this->get_data( $handle, 'group' );

		if ( false !== $group && $grp > $group )
			$grp = $group;

		return parent::set_group( $handle, $recursion, $grp );
	}

	/**
	 * Determines script dependencies.
     *
	 * @since 2.1.0
	 *
	 * @see WP_Dependencies::all_deps()
	 *
	 * @param mixed     $handles   Item handle and argument (string) or item handles and arguments (array of strings).
	 * @param bool      $recursion Internal flag that function is calling itself.
	 * @param int|false $group     Optional. Group level: (int) level, (false) no groups. Default false.
	 * @return bool True on success, false on failure.
	 */
	public function all_deps( $handles, $recursion = false, $group = false ) {
		$r = parent::all_deps( $handles, $recursion, $group );
		if ( ! $recursion ) {
			/**
			 * Filters the list of script dependencies left to print.
			 *
			 * @since 2.3.0
			 *
			 * @param array $to_do An array of script dependencies.
			 */
			$this->to_do = apply_filters( 'print_scripts_array', $this->to_do );
		}
		return $r;
	}

	/**
	 * Processes items and dependencies for the head group.
	 *
	 * @since 2.8.0
	 *
	 * @see WP_Dependencies::do_items()
	 *
	 * @return array Handles of items that have been processed.
	 */
	public function do_head_items() {
		$this->do_items(false, 0);
		return $this->done;
	}

	/**
	 * Processes items and dependencies for the footer group.
	 *
	 * @since 2.8.0
	 *
	 * @see WP_Dependencies::do_items()
	 *
	 * @return array Handles of items that have been processed.
	 */
	public function do_footer_items() {
		$this->do_items(false, 1);
		return $this->done;
	}

	/**
	 * Whether a handle's source is in a default directory.
	 *
	 * @since 2.8.0
	 *
	 * @param string $src The source of the enqueued script.
	 * @return bool True if found, false if not.
	 */
	public function in_default_dir( $src ) {
		if ( ! $this->default_dirs ) {
			return true;
		}

		if ( 0 === strpos( $src, '/' . WPINC . '/js/l10n' ) ) {
			return false;
		}

		foreach ( (array) $this->default_dirs as $test ) {
			if ( 0 === strpos( $src, $test ) ) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Resets class properties.
	 *
	 * @since 2.8.0
	 */
	public function reset() {
		$this->do_concat = false;
		$this->print_code = '';
		$this->concat = '';
		$this->concat_version = '';
		$this->print_html = '';
		$this->ext_version = '';
		$this->ext_handles = '';
	}
}