That is the case for an aria-describedby attribute. For example, some descriptions might be relevant only if referenced from the element they describe. However, in some cases elements might still link to HTML elements hidden in the CSS. The content marked with a hidden attribute should not be relevant to the user - otherwise it wouldn’t be hidden - and therefore there shouldn’t be any reason to link to it. This refers to, for example, the case of an href attribute linking to a hidden section. When using the HTML hidden attribute, it’s important you don’t link to the hidden element from non-hidden elements. It’s the perfect balance between SEO and UX Design. The strongest SEO benefit of hiding elements is the possibility of squeezing a lot of content onto a small mobile webpage while still delivering a smooth user experience. ![]() ![]() Lastly, a good reason to start using HTML hidden attributes is Google’s transition to a mobile-first index. Often in the case mentioned above, webmasters decide to use JavaScript to unblock the hidden elements, using something similar to the following: Source: Stack Overflow For example, you could hide certain elements of a page until the user completes the login process. It is often used to keep the user from seeing an element until some other requirement is fulfilled. The reason to hide an HTML element can vary. This means that if it is present, the value is always true, and if it’s absent, the value is always false. The HTML hidden attribute is a Boolean attribute. Normally, these would probably be provided by a service, but, for the purposes of this tutorial, you’ll find them in the Component class.Expert insight: A Boolean is a binary variable that can only have two possible values, 0 (false) or 1 (true). The list items are dynamically generated using an ngFor loop in the template. Each menu item is a link whose click is bound to the the onClick($event) method. The dropdown-menu DIV contains the ngClass directive that adds the menu-opened class whenever the menuOpened variable evaluates to true. The corresponding drop-down close happens in the dropdown-menu DIV’s click handler: For touchscreens, the click event duplicates the mouseenter action to display the drop-down. Hence, that takes care of devices with traditional screens. On click and mouseenter events, the menuOpened variable is set to true it is also set to false on mouseleave. In the HTML markup below, the menu-container DIV is the drop-down trigger. Rather than create a new project from scratch, we’ll just add a Menu link to the MatToolbar that we built in a previous tutorial: While a good choice if you require more advanced functionality, if you just want a simple DIY implementation, then the approach outlined here will do just fine! The Trigger Element The end result of today’s tutorial will be a menu that, in many ways, resembles the Angular Material MatMenu control. As you’ll see shortly, it can be something as simple as “ menu-opened”. One solution to this challenge is to replace CSS rules that rely on the :hover pseudo class with ones that include a class with a specific connotation that denotes the menu’s open state. ![]() This is a problem because once fired, triggering the correlated mouseleave event is not a trivial task. In many cases, they convert mouseenter events into clicks. However, touchscreens do not support hover events. On traditional screens, it’s nice to bind a drop-down menu’s visibility to the mouseenter and mouseleave events so that users don’t have to click the menu trigger to bring up the drop-down. Specifically, we’ll be using it to display a drop-down menu on both touch and traditional screens. Today, we’ll be exploring a specific use of NgClass to toggle an element’s visibility on and off according to user interactions. We learned all about its many permutations in the Assigning Dynamic Classes with NgClass article. In Angular applications, the NgClass directive is the de facto way to set CSS classes dynamically on DOM elements.
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