Refactor web worker implementation in main.js

src/main.js

@@ -1,18 +1,15 @@
-if (typeof SharedWorker === "undefined") {
-    alert('当前浏览器不支持webworker')
+if (typeof SharedWorker !== "undefined") {
+    const worker = new SharedWorker('/src/worker.js')
+    worker.port.onmessage = (e) => {
+        console.log('worker.port.onmessage:', e.data)
+    }
+    worker.port.start()
+    const button = document.createElement('button')
+    button.innerText = 'click'
+    button.onclick = () => {
+        worker.port.postMessage('hello, worker')
+    }
+    document.body.appendChild(button)
+} else {
+    console.log('当前浏览器不支持webworker')
 }
-
-// 检查是否存在其它标签页, 如果存在不必建立 websocket 连接, 如果不存在, 则建立 websocket 连接
-const worker = new SharedWorker('/src/worker.js')
-worker.port.onmessage = (e) => {
-    console.log('worker.port.onmessage:', e.data)
-}
-worker.port.start()
-
-const button = document.createElement('button')
-button.innerText = 'click'
-button.onclick = () => {
-    worker.port.postMessage('hello, worker')
-}
-
-document.body.appendChild(button)