HTMLLinkElement-impl.js
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"use strict";
const { reflectURLAttribute } = require("../../utils");
const DOMTokenList = require("../generated/DOMTokenList");
const HTMLElementImpl = require("./HTMLElement-impl").implementation;
const idlUtils = require("../generated/utils");
const { fetchStylesheet } = require("../helpers/stylesheets");
const { parseURLToResultingURLRecord } = require("../helpers/document-base-url");
const whatwgURL = require("whatwg-url");
// Important reading: "appropriate times to obtain the resource" in
// https://html.spec.whatwg.org/multipage/semantics.html#link-type-stylesheet
class HTMLLinkElementImpl extends HTMLElementImpl {
constructor(globalObject, args, privateData) {
super(globalObject, args, privateData);
this.sheet = null;
}
get relList() {
if (this._relList === undefined) {
this._relList = DOMTokenList.createImpl(this._globalObject, [], {
element: this,
attributeLocalName: "rel",
supportedTokens: new Set(["stylesheet"])
});
}
return this._relList;
}
_attach() {
super._attach();
maybeFetchAndProcess(this);
}
_attrModified(name, value, oldValue) {
super._attrModified(name, value, oldValue);
if (name === "href") { // TODO crossorigin="" or type=""
maybeFetchAndProcess(this);
}
if (name === "rel" && this._relList !== undefined) {
this._relList.attrModified();
}
}
get _accept() {
return "text/css,*/*;q=0.1";
}
get href() {
return reflectURLAttribute(this, "href");
}
set href(value) {
this.setAttributeNS(null, "href", value);
}
}
module.exports = {
implementation: HTMLLinkElementImpl
};
// https://html.spec.whatwg.org/multipage/links.html#link-type-stylesheet
function maybeFetchAndProcess(el) {
if (!isExternalResourceLink(el)) {
return;
}
// Browsing-context connected
if (!el.isConnected || !el._ownerDocument._defaultView) {
return;
}
fetchAndProcess(el);
}
// https://html.spec.whatwg.org/multipage/semantics.html#default-fetch-and-process-the-linked-resource
// TODO: refactor into general link-fetching like the spec.
function fetchAndProcess(el) {
const href = el.getAttributeNS(null, "href");
if (href === null || href === "") {
return;
}
const url = parseURLToResultingURLRecord(href, el._ownerDocument);
if (url === null) {
return;
}
// TODO handle crossorigin="", nonce, integrity="", referrerpolicy=""
const serialized = whatwgURL.serializeURL(url);
fetchStylesheet(el, serialized);
}
function isExternalResourceLink(el) {
// for our purposes, only stylesheets can be external resource links
const wrapper = idlUtils.wrapperForImpl(el);
if (!/(?:[ \t\n\r\f]|^)stylesheet(?:[ \t\n\r\f]|$)/i.test(wrapper.rel)) {
// rel is a space-separated list of tokens, and the original rel types
// are case-insensitive.
return false;
}
return Boolean(el.href);
}