How do you add a control in html?
Definition and UsageThe Show
When present, it specifies that audio/video controls should be displayed. Controls should include:
Applies toThe
ExamplesAudio ExampleAn
Try it Yourself » Video ExampleA
Try it Yourself » Browser SupportThe
❮ HTML ExampleA
Try it Yourself » Definition and UsageThe When present, it specifies that video controls should be displayed. Video controls should include:
Browser SupportThe numbers in the table specify the first browser version that fully supports the attribute.
Syntax❮ HTML There are some cases where the available native HTML form controls may seem like they are not enough. For example, if you need to perform advanced styling on some controls such as the In this article, we will discuss how to build a custom control. To that end, we will work with an example: rebuilding the Note: We'll focus on building the
control, not on how to make the code generic and reusable; that would involve some non-trivial JavaScript code and DOM manipulation in an unknown context, and that is out of the scope of this article. Before building a custom control, you should start by figuring out exactly what you want. This will save you some precious time. In particular, it's important to clearly define all the states of your control. To do this, it's good to start with an existing
control whose states and behavior are well known, so that you can mimic those as much as possible. In our example, we will rebuild the This screenshot shows the three main states of our control: the normal state (on the left); the active state (in the middle) and the open state (on the right). In terms of behavior, we are recreating a native HTML element. Therefore it should have the same behaviors and semantics as the native HTML element. We require our control to be usable with a mouse as well as with a keyboard, and comprehensible to a screen reader, just like any native control. Let's start by defining how the control reaches each state: The control is in its normal state when:
The control is in its active state when:
The control is in its open state when:
Once we know how to change states, it is important to define how to change the control's value: The value changes when:
The value does not change when:
Finally, let's define how the control's options will behave:
For the purposes of our example, we'll stop with that; however, if you're a careful reader, you'll notice that some behaviors are missing. For example, what do you think will happen if the user hits the tab key while the control is in its open state? The answer is nothing. OK, the right behavior seems obvious but the fact is, because it's not defined in our specs, it is very easy to overlook this behavior. This is especially true in a team environment when the people who design the control's behavior are different from the ones who implement it. Another fun example: what will happen if the user hits the up or down arrow keys while the control is in the open state? This one is a little bit trickier. If you consider that the active state and the open state are completely different, the answer is again "nothing will happen" because we did not define any keyboard interactions for the opened state. On the other hand, if you consider that the active state and the open state overlap a bit, the value may change but the option will definitely not be highlighted accordingly, once again because we did not define any keyboard interactions over options when the control is in its opened state (we have only defined what should happen when the control is opened, but nothing after that). We have to think a little further: what about the escape key? Pressing Esc key closes an open select.
Remember, if you want to provide the same functionality as the existing native In our example, the missing specifications are obvious so we will handle them, but it can be a real problem for exotic new controls. When it comes to standardized
elements, of which the Designing new interactions is generally only an option for very large industry players who have enough reach that an interaction they create can become a standard. For example, Apple introduced the scroll wheel with the iPod in 2001. They had the market share to successfully introduce a completely new way of interacting with a device, something most device companies can't do. It is best not to invent new user interactions. For any interaction you do add, it is vital to spend time in the design stage; if you define a behavior poorly, or forget to define one, it will be very hard to redefine it once the users have gotten used to it. If you have doubts, ask for the opinions of others, and if you have the budget for it, do not hesitate to perform user tests. This process is called UX Design. If you want to learn more about this topic, you should check out the following helpful resources:
Note: Also, in most systems there is a way to open the
Defining the HTML structure and (some) semanticsNow that the
control's basic functionality has been decided upon, it's time to start building it. The first step is to define its HTML structure and to give it some basic semantics. Here is what we need to rebuild a
Note the use of class names; these identify each relevant part regardless of the actual underlying HTML elements used. This is important to make sure that we
don't bind our CSS and JavaScript to a strong HTML structure, so that we can make implementation changes later without breaking code that uses the control. For example, what if you wish to implement the equivalent of the Class names, however, provide no semantic value. In this current state, the screen reader user only "sees" an unordered list. We will add ARIA semantics in a bit. Creating the look and feel using CSSNow that we have a structure, we can start designing our control. The whole point of building
this custom control is to be able to style it exactly how we want. To that end, we will split our CSS work into two parts: the first part will be the CSS rules absolutely necessary to make our control behave like a Required stylesThe required styles are those necessary to handle the three states of our control.
We need an extra class
Now, let's handle the list of options:
We need an extra class to handle when the list of options is hidden. This is necessary in order to manage the differences between the active state and the open state that do not exactly match.
Note: We could also have used BeautificationSo now that we have the basic functionality in place, the fun can start. The following is just an example of what is possible, and will match the screenshot at the beginning of this article. However, you should feel free to experiment and see what you can come up with.
We don't need an extra element to design the down arrow; instead, we're using the
Next, let's style the list of options:
For the
options, we need to add a
So here's the result with our three states: Bringing your control to life with JavaScriptNow that our design and structure are ready, we can write the JavaScript code to make the control actually work. Warning: The following is educational code, not production code, and should not be used as-is. It is neither future-proof nor will work on legacy browsers. It also has redundant parts that should be optimized in production code. Why isn't it working?Before starting, it's important to remember JavaScript in the browser is an unreliable technology. Custom controls rely on JavaScript to tie everything together. However, there are cases in which JavaScript isn't able to run in the browser:
Because of these risks, it's really important to seriously consider what will happen if your JavaScript doesn't work. We'll discuss options to consider and cover the basics in our example (a full discussion of solving this issue for all scenarios would require a book). Just remember, it is vital to make your script generic and reusable. In our example, if our JavaScript code isn't running, we'll fall back to displaying a standard To achieve this, we need two things: First, we need to add a regular
Second, we need two new classes to let us hide the unneeded element: we visually hide
the custom control if our script isn't running, or the "real"
This CSS visually hides one of the elements, but it is still available to screen readers. Now we need a JavaScript switch to determine if the script is running or not. This switch is a couple of lines: if at page
load time our script is running, it will remove the
Note: If you really want to make your code generic and reusable, instead of doing a class switch it's far better to just add the widget class to hide the
Making the job easierIn the code we are about to build, we will use the standard JavaScript and DOM APIs to do all the work we need. The features we plan to use are the following:
Building event callbacksThe groundwork is done. We can now start to define all the functions that will be used each time the user interacts with our control.
You need these in order to handle the various states of the custom control. Next, we bind these functions to the appropriate events:
At that point, our control will change state according to our design, but its value doesn't get updated yet. We'll handle that next. Handling the control's valueNow that our control is working, we have to add code to update its value according to user input and make it possible to send the value along with form data. The easiest way to do this is to use a native control under the hood. Such a control will keep track of the value with all the built-in controls provided by the browser, and the value will be sent as usual when a form is submitted. There's no point in reinventing the wheel when we can have all this done for us. As seen previously, we already use a native select control as a fallback for accessibility reasons; we can synchronize its value with that of our custom control:
With these two functions, we can bind the native controls to the custom ones:
In the code above, it's worth noting the use of the With that, we're done! Here's the result: But wait a second, are we really done? Making it accessibleWe have built something that works and though we're far from a fully-featured select box, it works nicely. But what we've done is nothing more than fiddle with the DOM. It has no real semantics, and even though it looks like a select box, from the browser's point of view it isn't one, so assistive technologies won't be able to understand it's a select box. In short, this pretty new select box isn't accessible! Fortunately, there is a solution and it's called ARIA. ARIA stands for "Accessible Rich Internet Application", and it's a W3C specification specifically designed for what we are doing here: making web applications and custom controls accessible. It's basically a set of attributes that extend HTML so that we can better describe roles, states and properties as though the element we've just devised was the native element it tries to pass for. Using these attributes can be done by editing the HTML markup. We also update the ARIA attributes via JavaScript as the user updates their selected value. The role attributeThe key attribute used by ARIA is the It's also worth noting that ARIA defines roles that are applied by default to standard HTML markup. For example, the To support the Note: Including both the Using the
The It might have seemed simpler to let a screen reader focus on the off-screen select and ignore our stylized one, but this is not an accessible solution. Screen readers are not limited to blind
people; people with low vision and even perfect vision use them as well. For this reason, you can not have the screen reader focus on an off-screen element. Here is the final result of all these changes (you'll get a better feel for this by trying it with an assistive technology such as NVDA or VoiceOver): If you want to
move forward, the code in this example needs some improvement before it becomes generic and reusable. This is an exercise you can try to perform. Two hints to help you in this: the first argument for all our functions is the same, which means those functions need the same context. Building an object to share that context would be wise. In the above example, we reinvented a We could therefore reinvent this using radio buttons instead; let's look at this option. We can start with a completely semantic, accessible, unordered list of radio buttons with an
associated We'll do a little styling of the radio button list (not the legend/fieldset) to
make it look somewhat like the earlier example, just to show that it can be done: With no JavaScript, and just a little bit of CSS, we are able to style the list of radio buttons to display only the checked item. When the focus is within the This works, to some extent, without JavaScript. We've created a similar control
to our custom control, that works even if the JavaScript fails. Looks like a great solution, right? Well, not 100%. It does work with the keyboard, but not as expected with a mouse click. It likely makes more sense to use web standards as the basis for custom controls instead of relying on frameworks to create elements with no native semantics. However, our control doesn't have the same functionality that a On the plus side, this control is fully accessible to a
screen reader and fully navigable via the keyboard. However, this control isn't a We'll
leave adding this missing functionality as a reader exercise. We have seen all the basics of building a custom form control, but as you can see it's not trivial to do. Before creating your own customized control, consider whether HTML
provides alternative elements that can be used to adequately support your requirements. If you do need to create a custom control, it is often easier to rely on third-party libraries instead of building your own. But, if you do create your own, modify existing elements, or use a framework to implement a pre-baked control, remember that creating a usable and accessible form control is more complicated than it looks. Here are a few libraries you should consider before coding your own: If you do create alternative controls via radio buttons, your own JavaScript, or with a 3rd party library, ensure it is accessible and
feature-proof; that is, it needs to be able to work better with a variety of browsers whose compatibility with the Web standards they use vary. Have fun! Bài Viết Liên QuanQuảng CáoCó thể bạn quan tâmCách sửa lỗi trong speakers properties ko hiện enhancement năm 20242 tháng trước . bởi MilitaryTracingToplist được quan tâm#1
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