Substitute the index generator into one function

src/utils/Utils.ts

@@ -78,13 +78,15 @@ export class Utils {
     public static generateIden (): string {
         let validIden: string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_';
         let ret: string = '';
+        
+        const idenIdx: (() => number) = () => Math.floor(Math.random() * validIden.length) % validIden.length;
 
-        ret += validIden[Math.floor(Math.random() * validIden.length) % validIden.length];
+        ret += validIden[idenIdx()];
         validIden += '0123456789';
         
         const len: number = Math.floor((Math.random() * 10) + 3);
         for (let i: number = 0; i < len; i++) {
-            ret += validIden[Math.floor(Math.random() * validIden.length) % validIden.length];
+            ret += validIden[idenIdx()];
         }
         
         return ret;