JavaScript outside the browser.
WHAT IT IS
A runtime executing JavaScript on the server.
WHY IT IS USED
One language across the stack An enormous package ecosystem Strong performance for input and output heavy work
WHAT THE CONCURRENCY MODEL IS
A single-threaded event loop, handling many connections by never waiting.
WHAT THAT MEANS
It excels at many concurrent connections doing little computation.
WHAT IT IS POOR AT
Heavy computation, which blocks everything.
WHAT BLOCKING LOOKS LIKE
Long loops Synchronous file operations Large synchronous parsing or encryption
WHAT TO DO ABOUT COMPUTATION
Move it to worker threads, a separate service, or a background queue.
WHAT MODULE SYSTEMS EXIST
The older format, and the standard module format.
WHAT TO PREFER
The standard format, for new work.
WHAT TO BE CAREFUL WITH
Mixing them, which produces confusing errors.
WHAT TO PIN
The runtime version, matching development and production.
WHY
Behaviour differs between versions, and mismatches produce failures only in production.
WHAT TO LEARN FIRST
Asynchronous patterns, modules, and the standard library.
