load initial page and display plain text

components/page.js

@@ -107,9 +107,22 @@ export class Page extends HTMLElement {
     const frames = wrap.getElementsByTagName('iframe')
     this.frame = frames[frames.length - 1]
     this.textArea.addEventListener('blur', e => {
-      const msg = ['srcdoc', e.target.value]
-this.frame.contentWindow.postMessage(msg, '*')
+      this.display(e.target.value)
     })
+    this.frame.addEventListener('load', () => {
+      this.display(this.body)
+    })
+  }
+
+  display(value) {
+    let doc = value
+    if (!(/<\w/).test(doc.substring(0, 30))) {
+      doc = `<pre style="white-space: pre-wrap; margin: 8px 12px; font-family: monospace;">` +
+        doc.replace("<", "&lt;").replace(">", "&gt;") +
+      `</pre>`
+    }
+    const msg = ['srcdoc', doc]
+    this.frame.contentWindow.postMessage(msg, '*')
   }
 
   set body(value) {