@@ -16,10 +16,10 @@ The reason for introducing a new “virtual” DOM is primarily:

a lean and stripped down virtual DOM can be used everywhere

* Most virtual DOMs do not focus on ease of use in transformations

* Other virtual DOMs cannot represent the syntax of HTML in its

entirety, think comments, document types, and character data

entirety (think comments, document types, and character data)

* Neither HTML nor virtual DOMs focus on positional information

**HAST** is a subset of [Unist][], and implemented by [rehype][].

**HAST** is a subset of [Unist][] and implemented by [rehype][].

This document may not be released. See [releases][] for released

documents. The latest released version is [`2.1.0`][latest].

@@ -223,22 +223,74 @@ interface Properties {}

##### Property names

Property names are keys on [`properties`][properties] objects and

reflect HTML attribute names. Often, they have the same value as

the corresponding HTML attribute (for example, `href` is a property

name reflecting the `href` attribute name).

If the HTML attribute name contains one or more dashes, the HAST

property name must be camel-cased (for example, `ariaLabel` is a

property reflecting the `aria-label` attribute).

If the HTML attribute is a reserved ECMAScript keyword, a common

alternative must be used. This is the case for `class`, which uses

`className` in HAST (and DOM), and `for`, which uses `htmlFor`.

> DOM uses other prefixes and suffixes too, for example, `relList`

> for HTML `rel` attributes. This does not occur in HAST.

When possible, HAST properties must be camel-cased if the HTML property

name originates from multiple words. For example, the `minlength` HTML

attribute is cased as `minLength`, and `typemustmatch` as `typeMustMatch`.

reflect HTML, SVG, ARIA, XML, XMLNS, or XLink attribute names.

Often, they have the same value as the corresponding attribute

(for example, `id` is a property name reflecting the `id` attribute

name), but there are some notable differences.

> These rules aren’t simple. Use [`hastscript`][h] (or

> [`property-information`][pi] directly) to help.

The following rules are used to disambiguate the names of attributes and their

corresponding HAST property name.

These rules are based on [how ARIA is reflected in the DOM][aria-dfn], and

differs from how some (older) HTML attributes are reflected in the DOM.

1. Any name referencing a combinations of multiple words (such as “stroke

miter limit”) becomes a camel-cased property name capitalising each word

boundary.

This includes combinations that are sometimes written as several words.

For example, `stroke-miterlimit` becomes `strokeMiterLimit`, `autocorrect`

becomes `autoCorrect`, and `allowfullscreen` becomes `allowFullScreen`.

2. Any name that can be hyphenated, becomes a camel-cased property name

capitalising each boundary.

For example, “read-only” becomes `readOnly`.

3. Compound words that are not used with spaces or hyphens are treated as a

normal word and the previous rules apply.

For example, “placeholder”, “strikethrough”, and “playback” stay the same.

4. Acronyms in names are treated as a normal word and the previous rules apply.

For example, `itemid` become `itemId` and `bgcolor` becomes `bgColor`.

###### Exceptions

Some jargon is seen as one word even though it may not be seen as such by

dictionaries.

For example, `nohref` becomes `noHref`, `playsinline` becomes `playsInline`,

and `accept-charset` becomes `acceptCharset`.

The HTML attributes `class` and `for` respectively become `className` and

`htmlFor` in alignment with the DOM.

No other attributes gain different names as properties, other than a change in

casing.

###### Notes

The HAST rules for property names differ from how HTML is reflected in the DOM

for the following attributes:

<details>

<summary>View list of differences</summary>

* `charoff` becomes `charOff` (not `chOff`)

* `char` stays `char` (does not become `ch`)

* `rel` stays `rel` (does not become `relList`)

* `checked` stays `checked` (does not become `defaultChecked`)

* `muted` stays `muted` (does not become `defaultMuted`)

* `value` stays `value` (does not become `defaultValue`)

* `selected` stays `selected` (does not become `defaultSelected`)

* `char` stays `char` (does not become `ch`)

* `allowfullscreen` becomes `allowFullScreen` (not `allowFullscreen`)

* `hreflang` becomes `hrefLang`, not `hreflang`

* `autoplay` becomes `autoPlay`, not `autoplay`

* `autocomplete` becomes `autoComplete` (not `autocomplete`)

* `autofocus` becomes `autoFocus`, not `autofocus`

* `enctype` becomes `encType`, not `enctype`

* `formenctype` becomes `formEncType` (not `formEnctype`)

* `vspace` becomes `vSpace`, not `vspace`

* `hspace` becomes `hSpace`, not `hspace`

* `lowsrc` becomes `lowSrc`, not `lowsrc`

</details>

##### Property values

@@ -247,13 +299,11 @@ property name. For example, the following HTML `<div hidden></div>`

contains a `hidden` (boolean) attribute, which is reflected as a `hidden`

property name set to `true` (boolean) as value in HAST, and

`<input minlength="5">`, which contains a `minlength` (valid

non-negative integer) attribute, is reflected as a property `minLength`

integer) attribute, is reflected as a property `minLength`

set to `5` (number) in HAST.

> In JSON, the property value `null` must be treated as if the

> property was not included.

> In JavaScript, both `null` and `undefined` must be similarly

> ignored.

> In JSON, the value `null` must be treated as if the property was not included.

> In JavaScript, both `null` and `undefined` must be similarly ignored.

The DOM is strict in reflecting those properties, and HAST is not,

where the DOM treats `<div hidden=no></div>` as having a `true`

@@ -262,7 +312,7 @@ as having a `0` (number) value for the `width` attribute, these should

be reflected as `'no'` and `'yes'`, respectively, in HAST.

> The reason for this is to allow plug-ins and utilities to inspect

> these values.

> these non-standard values.

The DOM also specifies comma- and space-separated lists attribute

values. In HAST, these should be treated as ordered lists.

@@ -444,3 +494,9 @@ Thanks to [**@kthjm**](https://github.com/kthjm)

[license]: https://creativecommons.org/licenses/by/4.0/

[author]: http://wooorm.com

[aria-dfn]: https://www.w3.org/TR/wai-aria-1.2/#idl_attr_disambiguation

[h]: https://github.com/syntax-tree/hastscript

[pi]: https://github.com/wooorm/property-information