svelte
Version:
Cybernetically enhanced web apps
68 lines (57 loc) • 2.11 kB
JavaScript
/** @import { TemplateNode } from '#client' */
import { hydrate_node, hydrating, set_hydrate_node, set_hydrating } from '../hydration.js';
import { create_text, get_first_child, get_next_sibling } from '../operations.js';
import { block } from '../../reactivity/effects.js';
import { HEAD_EFFECT } from '../../constants.js';
import { HYDRATION_START } from '../../../../constants.js';
/**
* @type {Node | undefined}
*/
let head_anchor;
export function reset_head_anchor() {
head_anchor = undefined;
}
/**
* @param {(anchor: Node) => void} render_fn
* @returns {void}
*/
export function head(render_fn) {
// The head function may be called after the first hydration pass and ssr comment nodes may still be present,
// therefore we need to skip that when we detect that we're not in hydration mode.
let previous_hydrate_node = null;
let was_hydrating = hydrating;
/** @type {Comment | Text} */
var anchor;
if (hydrating) {
previous_hydrate_node = hydrate_node;
// There might be multiple head blocks in our app, so we need to account for each one needing independent hydration.
if (head_anchor === undefined) {
head_anchor = /** @type {TemplateNode} */ (get_first_child(document.head));
}
while (
head_anchor !== null &&
(head_anchor.nodeType !== 8 || /** @type {Comment} */ (head_anchor).data !== HYDRATION_START)
) {
head_anchor = /** @type {TemplateNode} */ (get_next_sibling(head_anchor));
}
// If we can't find an opening hydration marker, skip hydration (this can happen
// if a framework rendered body but not head content)
if (head_anchor === null) {
set_hydrating(false);
} else {
head_anchor = set_hydrate_node(/** @type {TemplateNode} */ (get_next_sibling(head_anchor)));
}
}
if (!hydrating) {
anchor = document.head.appendChild(create_text());
}
try {
block(() => render_fn(anchor), HEAD_EFFECT);
} finally {
if (was_hydrating) {
set_hydrating(true);
head_anchor = hydrate_node; // so that next head block starts from the correct node
set_hydrate_node(/** @type {TemplateNode} */ (previous_hydrate_node));
}
}
}