node-- non-blocking I / O, single-threaded, asynchronous, event-driven

1, single-threaded

Unlike other backing languages, node is single-threaded, significant savings in server spending

node does not create a new thread for each client, only one thread. Non-blocking I / O and

Event-driven mechanism, it is complicated by the macro point of view, can handle high concurrency.

 

2, non-blocking I / O

1) When we encounter asynchronous, can be solved by the following methods:

① callback function

When using asynchronous function, chasing touching a callback function as a parameter passed to the callback required when using

The require FS = const ( 'FS' ) 

// how to solve the asynchronous problem? 
// Method 1: solved by callback 
function getContent (CB) { 
  fs.readFile ( 'a.txt', (ERR, Data) => {
     IF (ERR) { 
      the console.log (ERR) 
      return  to false 
    } 
    CB (Data ) 
  }) 
} 

getContent ((Data) => { 
  the console.log (data.toString ()) 
})

② module using the events to listen

The require FS = const ( 'FS' ) 
const Events = The require ( 'Events' ) 

// how to solve the asynchronous problem? 
@ Method 2: by the node modules events 

// we mainly performed by broadcasting and receiving a broadcast objects EventEmitter 
const = EventEmitter new new events.EventEmitter () 

// receive broadcast to_parent performs only listen 
function getContent () { 
  fs.readFile ( 'a.txt', (ERR, Data) => {
     IF (ERR) { 
      the console.log (ERR) 
      return  to false 
    } 
    EventEmitter.emit ( 'Data' , Data) 
  }) 
} 

getContent () 

EventEmitter.on ( ' data ', (data) => {
  console.log(data.toString())
})