completeBoundaryWithStyles() — react Function Reference

Source Code

packages/react-dom-bindings/src/server/fizz-instruction-set/ReactDOMFizzInstructionSetShared.js lines 451–575

export function completeBoundaryWithStyles(
  suspenseBoundaryID,
  contentID,
  stylesheetDescriptors,
) {
  const precedences = new Map();
  const thisDocument = document;
  let lastResource, node;

  // Seed the precedence list with existing resources and collect hoistable style tags
  const nodes = thisDocument.querySelectorAll(
    'link[data-precedence],style[data-precedence]',
  );
  const styleTagsToHoist = [];
  for (let i = 0; (node = nodes[i++]); ) {
    if (node.getAttribute('media') === 'not all') {
      styleTagsToHoist.push(node);
    } else {
      if (node.tagName === 'LINK') {
        window['$RM'].set(node.getAttribute('href'), node);
      }
      precedences.set(node.dataset['precedence'], (lastResource = node));
    }
  }

  let i = 0;
  const dependencies = [];
  let href, precedence, attr, loadingState, resourceEl, media;

  function cleanupWith(cb) {
    this['_p'] = null;
    cb();
  }

  // Sheets Mode
  let sheetMode = true;
  while (true) {
    if (sheetMode) {
      // Sheet Mode iterates over the stylesheet arguments and constructs them if new or checks them for
      // dependency if they already existed
      const stylesheetDescriptor = stylesheetDescriptors[i++];
      if (!stylesheetDescriptor) {
        // enter <style> Mode
        sheetMode = false;
        i = 0;
        continue;
      }

      let avoidInsert = false;
      let j = 0;
      href = stylesheetDescriptor[j++];

      if ((resourceEl = window['$RM'].get(href))) {
        // We have an already inserted stylesheet.
        loadingState = resourceEl['_p'];
        avoidInsert = true;
      } else {
        // We haven't already processed this href so we need to construct a stylesheet and hoist it
        // We construct it here and attach a loadingState. We also check whether it matches
        // media before we include it in the dependency array.
        resourceEl = thisDocument.createElement('link');
        resourceEl.href = href;
        resourceEl.rel = 'stylesheet';
        resourceEl.dataset['precedence'] = precedence =
          stylesheetDescriptor[j++];
        while ((attr = stylesheetDescriptor[j++])) {
          resourceEl.setAttribute(attr, stylesheetDescriptor[j++]);
        }
        loadingState = resourceEl['_p'] = new Promise((resolve, reject) => {
          resourceEl.onload = cleanupWith.bind(resourceEl, resolve);
          resourceEl.onerror = cleanupWith.bind(resourceEl, reject);
        });
        // Save this resource element so we can bailout if it is used again
        window['$RM'].set(href, resourceEl);
      }
      media = resourceEl.getAttribute('media');
      if (loadingState && (!media || window['matchMedia'](media).matches)) {
        dependencies.push(loadingState);
      }
      if (avoidInsert) {
        // We have a link that is already in the document. We don't want to fall through to the insert path