Ways to access the query parameters JSP, JSTL, Javascript
In the first approach you are accessing the request params using Scriptlets, definitely it works, but you have to make an additional check for null. Therefore Scriptlets are always avoided.
In the second approach using JSTLs, it is better than first approach, a refined version over scriptlets giving you more flexibility and robustness. So, it is something we would always encourage. This is the best approach of the three.
In the last approach, using Javascript, though another method; but never encouraged. It involves extra care to handle params carefully and you have better options to do the same job. Not an ideal task for Javascript to handle that!