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| Accessibility warnings |
Accessibility (shortened to a11y) isn't always easy to get right, but Svelte will help by warning you if you write inaccessible markup.
Here is a list of accessibility checks Svelte will do it for you.
a11y-accesskey
Enforce no accesskey on element. Access keys are HTML attributes that allow web developers to assign keyboard shortcuts to elements. Inconsistencies between keyboard shortcuts and keyboard commands used by screenreader and keyboard only users create accessibility complications so to avoid complications, access keys should not be used.
<!-- A11y: Avoid using accesskey -->
<div accessKey='z'></div>
a11y-aria-attributes
Certain reserved DOM elements do not support ARIA roles, states and properties. This is often because they are not visible, for example meta, html, script, style. This rule enforces that these DOM elements do not contain the aria-* props.
<!-- A11y: <meta> should not have aria-* attributes -->
<meta aria-hidden="false">
a11y-autofocus
Enforce that autofocus is not used on elements. Autofocusing elements can cause usability issues for sighted and non-sighted users, alike.
<!-- A11y: Avoid using autofocus -->
<input autofocus>
a11y-distracting-elements
Enforces that no distracting elements are used. Elements that can be visually distracting can cause accessibility issues with visually impaired users. Such elements are most likely deprecated, and should be avoided.
The following elements are visually distracting: <marquee> and <blink>.
<!-- A11y: Avoid <marquee> elements -->
<marquee />
a11y-hidden
Certain DOM elements are useful for screen readers navigation and should not be hidden.
<!-- A11y: <h2> element should not be hidden -->
<h2 aria-hidden>invisible header</h2>
a11y-img-redundant-alt
Enforce img alt attribute does not contain the word image, picture, or photo. Screenreaders already announce img elements as an image. There is no need to use words such as image, photo, and/or picture.
<img src="foo" alt="Foo eating a sandwich." />
<!-- aria-hidden, won't be announced by screen reader -->
<img src="bar" aria-hidden alt="Picture of me taking a photo of an image" />
<!-- A11y: Screenreaders already announce <img> elements as an image. -->
<img src="foo" alt="Photo of foo being weird." />
<!-- A11y: Screenreaders already announce <img> elements as an image. -->
<img src="bar" alt="Image of me at a bar!" />
<!-- A11y: Screenreaders already announce <img> elements as an image. -->
<img src="foo" alt="Picture of baz fixing a bug." />
a11y-invalid-attribute
Enforce that accessibility attribute should have valid value
<!-- A11y: '' is not a valid href attribute -->
<a href=''>invalid</a>
a11y-label-has-associated-control
Enforce that a label tag has a text label and an associated control.
There are two supported ways to associate a label with a control:
- Wrapping a control in a label tag.
- Adding
forto a label and assigning it a DOM ID string that indicates an input on the page.
<label for="id">B</label>
<label>C <input type="text" /></label>
<!-- A11y: A form label must be associated with a control. -->
<label>A</label>
a11y-media-has-caption
Providing captions for media is essential for deaf users to follow along. Captions should be a transcription or translation of the dialogue, sound effects, relevant musical cues, and other relevant audio information. Not only is this important for accessibility, but can also be useful for all users in the case that the media is unavailable (similar to alt text on an image when an image is unable to load).
The captions should contain all important and relevant information to understand the corresponding media. This may mean that the captions are not a 1:1 mapping of the dialogue in the media content. However, captions are not necessary for video components with the muted attribute.
<video><track kind="captions"/></video>
<audio muted></audio>
<!-- A11y: Media elements must have a <track kind=\"captions\"> -->
<video></video>
<!-- A11y: Media elements must have a <track kind=\"captions\"> -->
<video><track /></video>
a11y-misplaced-role
Certain reserved DOM elements do not support ARIA roles, states and properties. This is often because they are not visible, for example meta, html, script, style. This rule enforces that these DOM elements do not contain the role props.
<!-- A11y: <meta> should not have role attribute -->
<meta role="tooltip">
a11y-misplaced-scope
The scope scope should be used only on <th> elements.
<!-- A11y: The scope attribute should only be used with <th> elements -->
<div scope/>
a11y-missing-attribute
Enforce that element should have required accessibility attribute
<!-- A11y: <input type=\"image\"> element should have an alt, aria-label or aria-labelledby attribute -->
<input type="image">
<!-- A11y: <html> element should have a lang attribute -->
<html></html>
<!-- A11y: <a> element should have an href attribute -->
<a>text</a>
a11y-missing-content
Enforce that heading elements (h1, h2, etc.) and anchors have content and that the content is accessible to screen readers
<!-- A11y: <a> element should have child content -->
<a href='/foo'></a>
<!-- A11y: <h1> element should have child content -->
<h1></h1>
a11y-positive-tabindex
Avoid positive tabIndex property values to synchronize the flow of the page with keyboard tab order.
<!-- A11y: avoid tabindex values above zero -->
<div tabindex='1'/>
a11y-structure
Warns when accessibility related elements are not in a right structure.
<!-- A11y: <figcaption> must be an immediate child of <figure> -->
<div>
<figcaption>Image caption</figcaption>
</div>
a11y-unknown-aria-attribute
Invalid aria attribute. Enforces valid aria-* property based on WAI-ARIA States and Properties spec
<!-- A11y: Unknown aria attribute 'aria-labeledby' (did you mean 'labelledby'?) -->
<input type="image" aria-labeledby="foo">
a11y-unknown-role
Elements with ARIA roles must use a valid, non-abstract ARIA role. A reference to role definitions can be found at WAI-ARIA site.
<!-- A11y: Unknown role 'toooltip' (did you mean 'tooltip'?) -->
<div role="toooltip"></div>