nodeJS ReferenceError : navigator is not defined.

Hello I'm trying to make some Javascript files working on nodeJS everything is well set however here is the error I get :

C:\>node myServer.js

C:\myFunctionsCallTest.js:750
if( (j_lm && (navigator.appName == "Microsoft Internet Explorer")) || navigato
              ^
ReferenceError: navigator is not defined
    at Object.<anonymous> (C:\myFunctionsCallTest.js:750:15)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)
    at require (module.js:380:17)
    at Object.<anonymous> (C:\myServer.js:1:79)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)

C:\>

The files I'm using are :

myServer.js

var my_module = require("./myFunctionsCallTest.js");
console.log("RSA encrypted message :"+ my_module.Encrypt("myKey","myMessage"));

myFunctionsCallTest.js //This file contains some call of prototypes like : 
.....................................
RSAKey.prototype.setPublic = RSASetPublic;
RSAKey.prototype._short_encrypt = RSAEncrypt;
RSAKey.prototype.encrypt = RSAEncryptLong;
RSAKey.prototype.encrypt_b64 = RSAEncryptB64;
..............................................

Any idea from where this issue could come? Thanks.