Dynamic Navigation Menu

Most web applications feature a multi-page structure with a navigation menu to access different site sections. Typically positioned at the top or side of each page, these menus give users an easy way to explore content. In more complex applications, you may also encounter sub-menus, drop-downs, or side menus that help users navigate deeper content levels more effectively.

One easy way to build and manage these navigation structures is by using 'Server Side Includes'. This technique enhances component reuse in web development by allowing you to reuse HTML code across multiple pages. For instance, you can create a navigation bar, footer, or other common elements just once and then include them on any page as needed. This approach reduces repetitive code and boosts maintainability by keeping these shared components in a single file.

Beyond reusability, 'Server Side Includes' supports templating, which enables developers to inject dynamic data into HTML templates. With templating, you can maintain a consistent layout while populating pages with unique content. This separation between the application's logic and presentation results in cleaner, more organized code and enables the generation of dynamic, user-specific web pages.

By incorporating 'Server Side Includes', you simplify the construction of modern web applications and improve the user experience with efficient, dynamic navigation. Whether you're building a simple site or a complex dashboard, this technology provides robust tools for a flexible, user-friendly interface.

Designing the Dynamic Navigation Menu

In the figure below, the left image shows a typical web page that is part of a web application. The text in yellow shows where header data, such as CSS and JavaScript, the navigation menu, and the main page content should be located. We will go into detail on how to create a menu later on in this tutorial. The image to the right in the figure below shows how this page can be split into three components and then dynamically re-assembled at runtime by using server-side include. The reason we want to split this page into a "header", the main content, and a "footer", is that the header and footer are almost identical for all pages. We can reuse the header and footer on all pages for the web application by splitting the page up, as shown below, thus simplifying coding by reducing repetitive work. We will also minimize the size of the web application since we do not have to duplicate common code for each webpage in the application.

Figure 1: Shows how a page can be split up into three components, where common website code goes into the header and footer.

How to design the menu

HTML and CSS provide several options for creating a menu, and many of these options are based on HTML lists as shown below.

Figure 2: The HTML code for a menu and how the menu looks when CSS is not applied.

The menu does not look particularly attractive when Cascading Style Sheets (CSS) is not applied to it. The example below shows the same menu after applying CSS.

Figure 3: The menu from Figure 2 after applying CSS.

A complete explanation of how the CSS works for the above menu is beyond the scope of this tutorial, but a few things are worth noting. We used CSS3 for the above menu, and most new browsers today can handle CSS3. The menu will also work in older browsers but will have a dull look. The menu does not include any images. The gradient color is managed by using CSS3. Clicking a menu button inverts the color gradient order, and the button will appear to be pressed. You can find several online tools that can help you create CSS3 color gradients, and one such tool is the CSS Gradient Generator.

Dynamic header generation

We have so far shown you how to create a menu by using the HTML list element and styling it using CSS. The code for the menu in Figure 2 shows standard static HTML. We could have put this HTML into our header file that is to be included by all pages in our web application "as is", but the problem with this solution is that we would not see the selected (active) page visually in the menu. We want to have the selected page's menu button visually appear pressed. You can test this by clicking our test menu in Figure 3. The menu button you click should appear pressed. Having a pressed (selected) menu button for the active page makes it easier for the web application user to know what page is active. We mentioned above that the button appears pressed when we revert the gradient color order, and this can easily be achieved by creating a class for this purpose in the CSS. This class can then be applied to the selected page button.

<li><a class="selected" href="network.lsp">Network</a></li>

Figure 4: The menu button appears pressed when the "selected" class is set for the anchor element.

We only want the “selected” class on the menu button for the currently active webpage. Thus, our only option is to dynamically create the HTML for the menu. The following code fragment shows how to create the <li> elements in the menu.

 1 local links={
 2    {'network.lsp','Network'},
 3    {'security.lsp','Security'},
 4    {'users.lsp','Users'},
 5    {'admin.lsp','Admin'}
 6 }
 7 for index,link in ipairs(links) do
 8    local isactive -- Set isactive to true or false
 9    response:write('<li><a href="',link[1],'"',
10                   isactive and ' class="selected"' or '',
11                   '>',link[2],'</a></li>')
12 end

Figure 5: Shows how to dynamically create the <li> elements in the menu.

Line 1 to 5 declares a two-dimensional Lua array and this array includes all links and page titles for the web application.

Line 7 iterates over the outer array. The iterator returns the index position and the inner array. We have four elements in our outer array, so lines 8 to 11 will execute four times. The inner array contains the link and the page title.

Line 8 must set the variable isactive to true if the current page matches the current element in the array we are looping over. We will explain how this is done later.

Line 9 to 11 dynamically creates the <li> elements in the menu. Notice that we add the class "selected" to the <li> element to make the menu button appear pressed if variable isactive is true.

The only part missing in the puzzle is how to set the isactive variable on line 8. To do this, we first need to look at one of the pages in our web application that includes the header. The following example shows the network.lsp page.

 1 <?lsp title="Network" response:include".header.lsp" ?>
 2 <h1>Network</h1>
 3
 4 <?lsp response:include"footer.shtml" ?>

Figure 6: Shows the network.lsp page and how the LSP header file and the HTML footer file are included at runtime.

Notice the global variable assignment title="Network" on line 1 above. The Mako Server provides a short-lived global environment, and this environment is only active as long as the request is active. The global variable title will also be available when the .header.lsp file executes. The title is used on line 8 in Figure 5, and the correct code for this line in Figure 5 is as follows:

 8 local isactive = title == link[2]

The variable isactive is set to true in .header.lsp If the title set in the parent page matches the current title in the array we are looping over. The short-lived environment allows the parent page to set a variable for the included page. The short-lived environment is explained in the main documentation. See the Command (Request/Response) Environmment for details.

We also use the global title variable when emitting the HTML title element in .header.lsp:

<title><?lsp=title?></title>

Notice that the .header.lsp file name starts with a dot. File names that start with a dot are hidden and cannot be accessed via a browser. The file is only visible to server-side code such as to function response:include. The HTML footer page uses the extension shtml; this file is only visible to server-side code. The difference between the header and the footer is that the header is an LSP page and is executed on the server, and the footer is just a static HTML file.

HTML Templates

The menu we designed in this tutorial would typically be part of a website theme. Designing your own theme (or dashboard app) can be challenging, especially if you are new to CSS. We recommend having a web designer create a template for your website. A website template, such as a dashboard template, can easily be converted to a server-side generated website by splitting the template into three components, as explained in this tutorial. A custom-made template is recommended if you are designing a commercial product. You can also find many free templates on the Internet, but you must make sure you select a template that can easily be converted to a dynamic website. In other words, the template must include a menu that can be converted to a dynamically created server-side menu, as shown in this tutorial.

Conclusion

Many server technologies include support for server-side includes, including LSP, PHP, and Apache SSI. Many tools can pre-process HTML with embedded "HTML includes" directives and create static HTML. The web site css-tricks.com provides a list of several tools that can be used. However, "server-side includes" are best for sites with dynamically generated content, such as dashboard apps.

Creating a dashboard application using "server-side includes" is easy and a great solution for basic dashboard applications; however, one drawback is that every page needs server-side code at the top and bottom to include the header and footer. You may instead consider a solution based on the Model-View-Controller (MVC) design pattern for a more professional setup. Check out the tutorial, How to Build an Interactive Dashboard App, for a guide and a ready-to-use template code for your next project.

Posted in Tutorials by bd

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