[backend] fix: 修复异常处理和类型转换问题

frontend/node_modules/toggle-selection/example/demo.js

@@ -0,0 +1,16 @@
+var selection = document.getSelection();
+
+document.addEventListener('DOMContentLoaded', function(event) {
+  setTimeout(function() {
+    if (!selection.rangeCount) { // for demo purposes only
+      return;
+    }
+    reselect = module.exports();
+    setTimeout(function() {
+      reselect();
+      console.log('reselected');
+    }, 1000);
+
+    console.log('deselected');
+  }, 2000);
+});