Question: Is it possible to use client certificate for authentication in paho-mqtt javascript client?

From the application point of view, you will have only one option (set useSSL to true). Then Paho JavaScript client will establish a secure websocket connection (i.e. wss://) .
For two authentication, client requires a certificate to establish the connection.

Is it possible to use client authentication with a certificate instead of username/password with the Paho javascript client ? If so, how? please share the tutorials and documentation to proceed.

No files, tests, or entry points are mentioned. Start by reviewing the Paho JavaScript client's useSSL and secure WebSocket behavior, then verify whether browser-based client-certificate authentication is supported; done means providing accurate documentation or clearly stating the limitation and alternatives.

Written by the indexing model from the issue text.