My understand of why nodejs

Thread per connection VS Event loop

Advantage:
more memory consumption thread blocked waiting for I/O operation

• Q: So why not Event loop, callbacks, non-blocking I/O
• A: cultural and infrastructural.
  1. cultural, we thought that the I/O should be blocking.
  2. infrastructural
     • single threaded event loops require I/O to be non-blocking, but most libraries are not.
     • too much options: EventMachine, Twisted
• Q: Why javascript?
• A: javascript has the following features:
  1. Anonymous functions, closures. – easy to create callback
  2. Only one callback at a time. – only one callback at a time
  3. I/O through DOM event callbacks –non-blocking
  4. promise: a promise is a kind of EventEmitter which emits either “success” or “error”. (But not both.)