Tutorial Multi Level Push Menu

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An experimental push menu with multi-level functionality that allows endless nesting of navigation elements.

For sure you are familiar with the off-canvas navigation on mobile apps and the implementations for responsive websites like the one by David Bushell. We tried to explore the possibility of creating a nested multi-level menu, something that could be quite useful for menus with lots of content (like navigations of online stores). The result is a “push” menu that can (theoretically) contain infinite nested sub-menus. When opening a sub-level, the whole navigation pushes the content more, allowing a slice of the parent menu to be visible. Optionally, this slice can be visible or not, in which case the sub-menu will simply cover its parent.

Working with nested structures is quite tricky because when we, for example, move the parent then all children will of course move as well. So we are using a couple of tricks that will maintain the right 3D translates for the sub-menus and their children. The main idea is to increment the value for the translate so that we guarantee that the sub-levels are not shown once we push everything a bit more for showing the slices of the parents. This is of course not necessary in the case where the sub-menu is covering the parent menu.
Please note that we are using 3D Transforms which only work in modern browsers. You will find a fallback example for non-supporting browsers in the end of the component.css file where we simply show the first level menu. The same we do for the no JS case.
We are using the following nested structure for the menu:

<!-- mp-menu -->

<nav id="mp-menu" class="mp-menu">

    <div class="mp-level">

        <h2 class="icon icon-world">All Categories</h2>

        <ul>

            <li class="icon icon-arrow-left">

                <a class="icon icon-display" href="#">Devices</a>

                <div class="mp-level">

                    <h2 class="icon icon-display">Devices</h2>

                    <ul>

                        <li class="icon icon-arrow-left">

                            <a class="icon icon-phone" href="#">Mobile Phones</a>

                            <div class="mp-level">

                                <h2>Mobile Phones</h2>

                                <ul>

                                    <li><a href="#">Super Smart Phone</a></li>

                                    <li><a href="#">Thin Magic Mobile</a></li>

                                    <li><a href="#">Performance Crusher</a></li>

                                    <li><a href="#">Futuristic Experience</a></li>

                                </ul>

                            </div>

                        </li>

                        <li class="icon icon-arrow-left">

                            <!-- ... -->

                        </li>

                        <li class="icon icon-arrow-left">

                            <!-- ... -->

                        </li>

                    </ul>

                </div>

            </li>

            <li><!-- ... --></li>

            <!-- ... -->

        </ul>

    </div>

</nav>

<!-- /mp-menu -->

…where each level is wrapped into a division with the class mp-level.

Normally, we would have used fixed positioning for a menu of this kind but since there is quite an peculiar “problem” with that (transforms will make it behave like an absolute positioned element), we’ll have to use absolute positioning which will leave us with some unwanted behavior of the site (scrolling of menu and dependence of document height). So we’ve used a little trick to avoid the menu being scrollable or to be cut off if the site’s content is too short by using the following page structure:

<div class="container">

    <!-- Push Wrapper -->

    <div class="mp-pusher" id="mp-pusher">

        <!-- mp-menu -->

        <nav id="mp-menu" class="mp-menu">

            <!-- ... -->

        </nav>

        <!-- /mp-menu -->

        <div class="scroller"><!-- this is for emulating position fixed of the nav -->

            <div class="scroller-inner">

                <!-- site content goes here -->

                </div>

            </div><!-- /scroller-inner -->

        </div><!-- /scroller -->

    </div><!-- /pusher -->

</div><!-- /container -->

Where we set the following styles for the elements:

html, 

body, 

.container,

.scroller {

    height: 100%;

}

.scroller {

    overflow-y: scroll;

}

.scroller,

.scroller-inner {

    position: relative;

}

.container {

    position: relative;

    overflow: hidden;

    background: #34495e;

}

This will allow the content to be scrolled when the menu is closed and it will also make the menu being 100% of the window height. Basically, we are emulating what fixed positioning would do here.
This is how the plugin can be called:

new mlPushMenu( document.getElementById( 'mp-menu' ), document.getElementById( 'trigger' ) );

Or, if the submenus should cover the previous levels: 

new mlPushMenu( document.getElementById( 'mp-menu' ), document.getElementById( 'trigger' ), {

    type : 'cover'

} );