Juniper has created some 2 1/2 hour versions of introductory classes. These are recorded webinars that are available for free after registration.
These are the on-demand free Junos Jump Start webinars.
Fundamentals (brocade translation)
This focuses on data center switching applications and translation of Brocade functionality. But is also a good introduction to the switching setup in general.
Intermediate – routing focus
This covers static, OSPF and BGP topics.
Advanced – OSPF & BGP Features
This continues the routing focus with more advanced features in OSPF and BGP.
This is basic campus layer 2 switching, STP and related configurations.
Introduction to the SRX and the Junos flow module that has full session based firewall and NGFW features.
Introduction to automation with the focus on Ansible and PyEZ as the tools.