diff --git a/src/base32.js b/src/base32.js
index 815947e..af7022c 100644
--- a/src/base32.js
+++ b/src/base32.js
@@ -4,12 +4,12 @@
  *  @author   : Gin (gin.lance.inside@hotmail.com)
  */
 
- export default class Base32 {
+ export class Base32 {
     static decode() {
-        console.log("static Base32.decode");
+        return "static Base32.decode";
     }
 
     static random_gen() {
-        console.log("static Base32.random_gen");
+        return "static Base32.random_gen";
     }
  }
\ No newline at end of file
diff --git a/src/hotp.js b/src/hotp.js
index 00c08b2..484a6e3 100644
--- a/src/hotp.js
+++ b/src/hotp.js
@@ -5,7 +5,7 @@
 
 import OTP from './otp';
 
-export default class HOTP extends OTP {
+export class HOTP extends OTP {
     /*＊
      * Generate the OTP with the given count
      *
@@ -22,7 +22,7 @@ export default class HOTP extends OTP {
      * ```
      */
     at(count) {
-        console.log("HOTP.at");
+        return "HOTP.at";
     }
 
     /*＊
@@ -47,6 +47,6 @@ export default class HOTP extends OTP {
      * ```
      */
     verify(otp, counter) {
-        console.log("HOTP.verify");
+        return "HOTP.verify";
     }
 }
\ No newline at end of file
diff --git a/src/otp.js b/src/otp.js
index 1c33994..15428e5 100644
--- a/src/otp.js
+++ b/src/otp.js
@@ -3,7 +3,7 @@
  *  @author   : Gin (gin.lance.inside@hotmail.com)
  */
 
-export default class OTP  {
+export class OTP  {
     /*＊
      * This constructor will create OTP instance.
      *
@@ -41,7 +41,7 @@ export default class OTP  {
      * @return {OTP}
      */
     generate_otp(input) {
-        console.log("OTP.generate_otp");
+        return "OTP.generate_otp";
     }
  }
 
diff --git a/src/totp.js b/src/totp.js
index eebbec9..beeba1e 100644
--- a/src/totp.js
+++ b/src/totp.js
@@ -5,7 +5,7 @@
 
 import OTP from './otp';
 
-export default class TOTP extends OTP {
+export class TOTP extends OTP {
     /*＊
      * @param {secret}
      * @type {String} 
@@ -35,7 +35,7 @@ export default class TOTP extends OTP {
      * ```
      */
     now() {
-        console.log("TOTP.now");
+        return "TOTP.now";
     }
 
     /*＊
@@ -62,6 +62,6 @@ export default class TOTP extends OTP {
      * ```
      */
     verify(otp, time=null) {
-        console.log("TOTP.verify");
+        return "TOTP.verify";
     }
  }
\ No newline at end of file