Fetch tracers.js from unpkg instead of from github release

src/tracers/js/JsTracer.ts

@@ -1,26 +1,27 @@
 import path from 'path';
-import { download } from 'utils/misc';
 import { Release, Tracer } from 'tracers/Tracer';
 import express from 'express';
-import { publicDir } from 'config/paths';
 
 export class JsTracer extends Tracer {
-  readonly tracerPath: string;
   readonly workerPath: string;
+  tagName?: string;
 
   constructor() {
     super('js');
-    this.tracerPath = path.resolve(publicDir, 'algorithm-visualizer.js');
     this.workerPath = path.resolve(__dirname, 'worker.js');
   }
 
-  build(release: Release) {
+  async build(release: Release) {
     const {tag_name} = release;
-    return download(`https://github.com/algorithm-visualizer/tracers.js/releases/download/${tag_name}/algorithm-visualizer.js`, this.tracerPath);
+    this.tagName = tag_name;
   }
 
   route(router: express.Router) {
-    router.get(`/${this.lang}`, (req, res) => res.sendFile(this.tracerPath));
+    router.get(`/${this.lang}`, (req, res) => {
+      if (!this.tagName) throw new Error('JsTracer has not been built yet.');
+      const version = this.tagName.slice(1);
+      res.redirect(`https://unpkg.com/algorithm-visualizer@${version}/dist/index.umd.js`);
+    });
     router.get(`/${this.lang}/worker`, (req, res) => res.sendFile(this.workerPath));
   }
 }