fix build

Author: shanghaikid

server/src/utils/Helper.ts

@@ -45,9 +45,9 @@ export const genRows = (fields: FieldSchema[], size: number) => {
 
 export const makeRandomId = (length: number): string => {
   var result = '';
-  var characters =
+  const characters =
     'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
-  var charactersLength = characters.length;
+  const charactersLength = characters.length;
   for (var i = 0; i < length; i++) {
     result += characters.charAt(Math.floor(Math.random() * charactersLength));
   }