conventions.js

'use strict'

/**
 * "Shallow freezes" an object to render it immutable.
 * Uses `Object.freeze` if available,
 * otherwise the immutability is only in the type.
 *
 * Is used to create "enum like" objects.
 *
 * @template T
 * @param {T} object the object to freeze
 * @param {Pick<ObjectConstructor, 'freeze'>} [oc=Object] `Object` by default,
 * 				allows to inject custom object constructor for tests
 * @returns {Readonly<T>}
 *
 * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze
 */
function freeze(object, oc) {
	if (oc === undefined) {
		oc = Object
	}
	return oc && typeof oc.freeze === 'function' ? oc.freeze(object) : object
}

/**
 * Since we can not rely on `Object.assign` we provide a simplified version
 * that is sufficient for our needs.
 *
 * @param {Object} target
 * @param {Object | null | undefined} source
 *
 * @returns {Object} target
 * @throws TypeError if target is not an object
 *
 * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
 * @see https://tc39.es/ecma262/multipage/fundamental-objects.html#sec-object.assign
 */
function assign(target, source) {
	if (target === null || typeof target !== 'object') {
		throw new TypeError('target is not an object')
	}
	for (var key in source) {
		if (Object.prototype.hasOwnProperty.call(source, key)) {
			target[key] = source[key]
		}
	}
	return target
}

/**
 * A number of attributes are boolean attributes.
 * The presence of a boolean attribute on an element represents the `true` value,
 * and the absence of the attribute represents the `false` value.
 *
 * If the attribute is present, its value must either be the empty string
 * or a value that is an ASCII case-insensitive match for the attribute's canonical name,
 * with no leading or trailing whitespace.
 *
 * Note: The values `"true"` and `"false"` are not allowed on boolean attributes.
 * To represent a `false` value, the attribute has to be omitted altogether.
 *
 * @see https://html.spec.whatwg.org/#boolean-attributes
 * @see https://html.spec.whatwg.org/#attributes-3
 */
var HTML_BOOLEAN_ATTRIBUTES = freeze({
	allowfullscreen: true,
	async: true,
	autofocus: true,
	autoplay: true,
	checked: true,
	controls: true,
	default: true,
	defer: true,
	disabled: true,
	formnovalidate: true,
	hidden: true,
	ismap: true,
	itemscope: true,
	loop: true,
	multiple: true,
	muted: true,
	nomodule: true,
	novalidate: true,
	open: true,
	playsinline: true,
	readonly: true,
	required: true,
	reversed: true,
	selected: true,
})

/**
 * Check if `name` is matching one of the HTML boolean attribute names.
 * This method doesn't check if such attributes are allowed in the context of the current document/parsing.
 *
 * @param {string} name
 * @return {boolean}
 * @see HTML_BOOLEAN_ATTRIBUTES
 * @see https://html.spec.whatwg.org/#boolean-attributes
 * @see https://html.spec.whatwg.org/#attributes-3
 */
function isHTMLBooleanAttribute(name) {
	return HTML_BOOLEAN_ATTRIBUTES.hasOwnProperty(name.toLowerCase())
}

/**
 * Void elements only have a start tag; end tags must not be specified for void elements.
 * These elements should be written as self closing like this: `<area />`.
 * This should not be confused with tags that HTML allows to omit the end tag for
 * (like `li`, `tr` and others), which have content after them,
 * so they can not be written as self closing.
 * (xmldom does not have any logic for ommitable cases and will report them as a warning.)
 *
 * @type {Readonly<{area: boolean, col: boolean, img: boolean, wbr: boolean, link: boolean, hr: boolean, source: boolean, br: boolean, input: boolean, param: boolean, meta: boolean, embed: boolean, track: boolean, base: boolean}>}
 * @see https://html.spec.whatwg.org/#void-elements
 */
var HTML_VOID_ELEMENTS = freeze({
	area: true,
	base: true,
	br: true,
	col: true,
	embed: true,
	hr: true,
	img: true,
	input: true,
	link: true,
	meta: true,
	param: true,
	source: true,
	track: true,
	wbr: true,
})

/**
 * Check if `tagName` is matching one of the HTML void element names.
 * This method doesn't check if such tags are allowed
 * in the context of the current document/parsing.
 *
 * @param {string} tagName
 * @return {boolean}
 * @see HTML_VOID_ELEMENTS
 */
function isHTMLVoidElement(tagName) {
	return HTML_VOID_ELEMENTS.hasOwnProperty(tagName.toLowerCase())
}

/**
 * Tag names that are raw text elements according to HTML spec.
 * The value denotes whether they are escapable or not.
 *
 * @see isHTMLEscapableRawTextElement
 * @see isHTMLRawTextElement
 * @see https://html.spec.whatwg.org/#raw-text-elements
 * @see https://html.spec.whatwg.org/#escapable-raw-text-elements
 */
var HTML_RAW_TEXT_ELEMENTS = freeze({
	script: false,
	style: false,
	textarea: true,
	title: true,
})

/**
 * Check if `tagName` is matching one of the HTML raw text element names.
 * It includes escapable and not escapable raw text elements.
 * This method doesn't check if such tags are allowed
 * in the context of the current document/parsing.
 *
 * @param {string} tagName
 * @return {boolean}
 * @see HTML_RAW_TEXT_ELEMENTS
 * @see https://html.spec.whatwg.org/#raw-text-elements
 * @see https://html.spec.whatwg.org/#escapable-raw-text-elements
 */
function isHTMLRawTextElement(tagName) {
	return HTML_RAW_TEXT_ELEMENTS.hasOwnProperty(tagName.toLowerCase())
}
/**
 * Check if `tagName` is matching one of the HTML escapable raw text element names.
 * This method doesn't check if such tags are allowed
 * in the context of the current document/parsing.
 *
 * @param {string} tagName
 * @return {boolean}
 * @see isHTMLRawTextElement
 * @see HTML_RAW_TEXT_ELEMENTS
 * @see https://html.spec.whatwg.org/#raw-text-elements
 * @see https://html.spec.whatwg.org/#escapable-raw-text-elements
 */
function isHTMLEscapableRawTextElement(tagName) {
	const key = tagName.toLowerCase();
	return HTML_RAW_TEXT_ELEMENTS.hasOwnProperty(key) && HTML_RAW_TEXT_ELEMENTS[key];
}

/**
 * All mime types that are allowed as input to `DOMParser.parseFromString`
 *
 * @see https://developer.mozilla.org/en-US/docs/Web/API/DOMParser/parseFromString#Argument02 MDN
 * @see https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#domparsersupportedtype WHATWG HTML Spec
 * @see DOMParser.prototype.parseFromString
 */
var MIME_TYPE = freeze({
	/**
	 * `text/html`, the only mime type that triggers treating an XML document as HTML.
	 *
	 * @see DOMParser.SupportedType.isHTML
	 * @see https://www.iana.org/assignments/media-types/text/html IANA MimeType registration
	 * @see https://en.wikipedia.org/wiki/HTML Wikipedia
	 * @see https://developer.mozilla.org/en-US/docs/Web/API/DOMParser/parseFromString MDN
	 * @see https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#dom-domparser-parsefromstring WHATWG HTML Spec
	 */
	HTML: 'text/html',

	/**
	 * Helper method to check a mime type if it indicates an HTML document
	 *
	 * @param {string} [value]
	 * @returns {boolean}
	 *
	 * @see [IANA MimeType registration](https://www.iana.org/assignments/media-types/text/html)
	 * @see [Wikipedia](https://en.wikipedia.org/wiki/HTML)
	 * @see [`DOMParser.parseFromString` @ MDN](https://developer.mozilla.org/en-US/docs/Web/API/DOMParser/parseFromString)
	 * @see [`DOMParser.parseFromString` @ HTML Specification](https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#dom-domparser-parsefromstring)
	 */
	isHTML: function (value) {
		return value === MIME_TYPE.HTML
	},

	/**
	 * For both the `text/html` and the `application/xhtml+xml` namespace
	 * the spec defines that the HTML namespace is provided as the default in some cases.
	 *
	 * @param {string} mimeType
	 * @returns {boolean}
	 *
	 * @see https://dom.spec.whatwg.org/#dom-document-createelement
	 * @see https://dom.spec.whatwg.org/#dom-domimplementation-createdocument
	 * @see https://dom.spec.whatwg.org/#dom-domimplementation-createhtmldocument
	 */
	hasDefaultHTMLNamespace: function (mimeType) {
		return (
			MIME_TYPE.isHTML(mimeType) || mimeType === MIME_TYPE.XML_XHTML_APPLICATION
		)
	},

	/**
	 * `application/xml`, the standard mime type for XML documents.
	 *
	 * @see https://www.iana.org/assignments/media-types/application/xml IANA MimeType registration
	 * @see https://tools.ietf.org/html/rfc7303#section-9.1 RFC 7303
	 * @see https://en.wikipedia.org/wiki/XML_and_MIME Wikipedia
	 */
	XML_APPLICATION: 'application/xml',

	/**
	 * `text/html`, an alias for `application/xml`.
	 *
	 * @see https://tools.ietf.org/html/rfc7303#section-9.2 RFC 7303
	 * @see https://www.iana.org/assignments/media-types/text/xml IANA MimeType registration
	 * @see https://en.wikipedia.org/wiki/XML_and_MIME Wikipedia
	 */
	XML_TEXT: 'text/xml',

	/**
	 * `application/xhtml+xml`, indicates an XML document that has the default HTML namespace,
	 * but is parsed as an XML document.
	 *
	 * @see https://www.iana.org/assignments/media-types/application/xhtml+xml IANA MimeType registration
	 * @see https://dom.spec.whatwg.org/#dom-domimplementation-createdocument WHATWG DOM Spec
	 * @see https://en.wikipedia.org/wiki/XHTML Wikipedia
	 */
	XML_XHTML_APPLICATION: 'application/xhtml+xml',

	/**
	 * `image/svg+xml`,
	 *
	 * @see https://www.iana.org/assignments/media-types/image/svg+xml IANA MimeType registration
	 * @see https://www.w3.org/TR/SVG11/ W3C SVG 1.1
	 * @see https://en.wikipedia.org/wiki/Scalable_Vector_Graphics Wikipedia
	 */
	XML_SVG_IMAGE: 'image/svg+xml',
})

/**
 * Namespaces that are used in this code base.
 *
 * @see http://www.w3.org/TR/REC-xml-names
 */
var NAMESPACE = freeze({
	/**
	 * The XHTML namespace.
	 *
	 * @see http://www.w3.org/1999/xhtml
	 */
	HTML: 'http://www.w3.org/1999/xhtml',

	/**
	 * Checks if `uri` equals `NAMESPACE.HTML`.
	 *
	 * @param {string} [uri]
	 *
	 * @see NAMESPACE.HTML
	 */
	isHTML: function (uri) {
		return uri === NAMESPACE.HTML
	},

	/**
	 * The SVG namespace.
	 *
	 * @see http://www.w3.org/2000/svg
	 */
	SVG: 'http://www.w3.org/2000/svg',

	/**
	 * The `xml:` namespace.
	 *
	 * @see http://www.w3.org/XML/1998/namespace
	 */
	XML: 'http://www.w3.org/XML/1998/namespace',

	/**
	 * The `xmlns:` namespace
	 *
	 * @see https://www.w3.org/2000/xmlns/
	 */
	XMLNS: 'http://www.w3.org/2000/xmlns/',
})

exports.assign = assign
exports.freeze = freeze
exports.HTML_BOOLEAN_ATTRIBUTES = HTML_BOOLEAN_ATTRIBUTES
exports.HTML_RAW_TEXT_ELEMENTS = HTML_RAW_TEXT_ELEMENTS
exports.HTML_VOID_ELEMENTS = HTML_VOID_ELEMENTS
exports.isHTMLBooleanAttribute = isHTMLBooleanAttribute
exports.isHTMLRawTextElement = isHTMLRawTextElement
exports.isHTMLEscapableRawTextElement = isHTMLEscapableRawTextElement
exports.isHTMLVoidElement = isHTMLVoidElement
exports.MIME_TYPE = MIME_TYPE
exports.NAMESPACE = NAMESPACE