when the suitelet url change? in training they have mentioned that it changes after some modification

The base URL will only change if you make a different deployment or script record of your suitelet script.

yeah but he said that to use resolvescript rather than hardcoding because the URL might change because of changes in the script. i guess he phrased wrong then

I think that was more likely before account specific domains happened. Even still, it would be better to use

resolvescript

when you can to ensure you stay abstracted from any changes they might decide to make.

Using N.url.resolveScript method is good practise because if the script will be copied between accounts, then the base URL may change. For example, a sandbox refresh.

gotcha