Add Store.parseMetaTags

Author: joepio

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 This changelog covers all three packages, as they are (for now) updated as a whole
 
+## UNRELEASED
+
+- Add `Store.parseMetaTags` to load JSON-AD objects stored in the DOM. Speeds up initial page load by allowing server to set JSON-AD objects in the initial HTML response.
+
 ## v0.35.0
 
 ### @tomic/react

data-browser/src/App.tsx

@@ -40,6 +40,8 @@ const store = new Store({
   serverUrl,
 });
 
+store.parseMetaTags();
+
 declare global {
   interface Window {
     bugsnagApiKey: string;

lib/src/store.ts

@@ -9,6 +9,7 @@ import {
   unknownSubject,
   urls,
   Commit,
+  JSONADParser,
 } from './index.js';
 import { authenticate, fetchWebSocket, startWebsocket } from './websockets.js';
 
@@ -412,6 +413,28 @@ export class Store {
     this.eventManager.emit(StoreEvents.ResourceManuallyCreated, resource);
   }
 
+  /** Parses the HTML document for `JSON-AD` data in <meta> tags, adds it to the store */
+  public parseMetaTags(): void {
+    const metaTags = document.querySelectorAll(
+      'meta[property="json-ad-initial"]',
+    );
+    const parser = new JSONADParser();
+
+    metaTags.forEach(tag => {
+      const content = tag.getAttribute('content');
+
+      if (content === null) {
+        return;
+      }
+
+      // convert base64 content to JSON
+      const json = JSON.parse(atob(content));
+
+      const [_, resources] = parser.parseObject(json);
+      this.addResources(...resources);
+    });
+  }
+
   /** Removes (destroys / deletes) resource from this store */
   public removeResource(subject: string): void {
     const resource = this.resources.get(subject);