We all know Node is single threaded, however, it's single threaded for a client (to you as a programmer), but the platform itself is multi-threaded (internally). In order to check how many threads your node is using on Linux machine you have 3 different options:

1.

cat /proc/`pidof node`/status | grep Threads

2.

ls /proc/19899/task/ | wc -l

3.

ps hH p `pidof node` | wc -l

Sometimes, it come in handy when you want to automate the load monitoring for example.