Is automatically assigning focus bad for accessibility?

If I have a form that is the main part of a page's content, 开发者_如何学JAVAwill assigning focus to the first form field via JavaScript on page load have any negative effects on accessibility?

The short answer is no it doesn't make things inaccessible but it can make it confusing. The longer answer follows. Will your users know that there going to a page with a form, and does there need to be any descriptive text you should read before filling out the form? I'm a screen reader user and it can be annoying having focused put in random fields. It's clear why your focus winds up in the Google search box so that doesn't bother me. If my focus were automatically placed in the answer edit field every time I viewed a question on Stackoverflow I would be annoyed since I'd have to force my screen reader to navigate away from the form field and to the top of the page.

It might a bit, if we've got a keyboard user (either using a screen-reader, or just a habitual keyboard user) who's expecting to be navigating the links at the top of the page on first Tab press. For screen readers, you could also consider adding WAI-ARIA to add directions if users who don't expect to be dumped into the middle of a form.

If it's much more likely that the user's going to be wanting to type in the field straight away, then I think the autofocus is worth it. But for the reason above I wouldn't use it on every page with an input field.

If you do autofocus, make sure to do it right away, in a script as soon as possible following the input element, or in future using the HTML5 autofocus attribute. Don't do it as late as window.onload. It's annoying to have clicked the focus elsewhere only to have the document belatedly finish loading and steal the focus onto another element as you type.

A lot of sites will do this, google is a good example, the only issue is when you are typing something into the address bar, or into the search input in your browser, the action of focusing the form field tends to steal focus from where you are typing. It's a small nuisance.

will assigning focus to the first form field via JavaScript on page load have any negative effects on accessibility?

I can't think of any. In between fields might irritate whatever assistive software a user might be running, but the first field - hardly. I have no experience with braille and similar clients.

Seeing as even Google do it on their front page, I don't think it can be that big a deal either way.

Quoting MDN autofocus -> accessibility considerations (retrieved 9/28/2022):

Automatically focusing a form control can confuse visually-impaired people using screen-reading technology and people with cognitive impairments. When autofocus is assigned, screen-readers "teleport" their user to the form control without warning them beforehand.

Use careful consideration for accessibility when applying the autofocus attribute. Automatically focusing on a control can cause the page to scroll on load. The focus can also cause dynamic keyboards to display on some touch devices. While a screen reader will announce the label of the form control receiving focus, the screen reader will not announce anything before the label, and the sighted user on a small device will equally miss the context created by the preceding content.

To add some practical examples, at the time of writing, https://www.google.com autofocuses on the search box, while Wikipedia and Amazon don't. If typing into a search box is the sole purpose of the page and the risk of confusion is low, then it's worth considering autofocusing on it. Otherwise, probably skip autofocusing.

I wouldn't say so, fragments are an ingredient of HTTP and they set the focus of an *html page..

I wouldn't say so. A screenreader will probably not even notice this since it doesn't interpret the JavaScript on the page.

Another user which has a "normal" browser will get the advantage of having the cursor already at the right place which facilitates the navigation by using just the keyboard.