ESP8266 - Uncaught Error: Field or method does not already exist, and can't create it on undefined

Thanks for your response, but no way, it didn't worked again. I'm giving up for now.
Here is the error message :

Uncaught Error: No Acknowledgement  at line 1 col 46 var wifi = require("ESP8266").connect(Serial4);
                                              ^ Uncaught Error: Field or method does not already exist, and can't create it on undefined  at line 2 col 5 wifi.connect("WiFi_Name","WPA2_Key", function() {
     ^ in function called from system