diff --git a/docs/demo/index.js b/docs/demo/index.js
index 90e501596..4299e3013 100644
--- a/docs/demo/index.js
+++ b/docs/demo/index.js
@@ -4,3 +4,6 @@ dayjs().format()
 
 // parse
 dayjs('2018-08-08').format()
+
+// format
+dayjs().format('YYYY-MM-DD')