diff --git a/js/freq.ts b/js/freq.ts
index e795b49..bd90f49 100644
--- a/js/freq.ts
+++ b/js/freq.ts
@@ -7,3 +7,13 @@ typeof '' === 'string';
 'blue ss'.indexOf('blue');
 
 // str.substring(indexStart[, indexEnd])
+
+
+// 向下取整 floor
+Math.floor( 45.95); // 45
+// 向上取整 ceil
+Math.ceil(.95) // 1
+
+// 给定数字的值四舍五入到最接近的整数。
+Math.round(20.49);   //20
+Math.round(20.5);    //21