diff --git a/docs/symbol.md b/docs/symbol.md
index 567368a..7e2b351 100644
--- a/docs/symbol.md
+++ b/docs/symbol.md
@@ -492,6 +492,13 @@ class Even {
   }
 }
 
+// 等同于
+const Even = {
+  [Symbol.hasInstance](obj) {
+    return Number(obj) % 2 === 0;
+  }
+};
+
 1 instanceof Even // false
 2 instanceof Even // true
 12345 instanceof Even // false