A shallow understanding of node. js

Recently began to learn about node. js, here to see the recent (Seven days learn Nodejs) about a string, deepen understanding.

node. JS is a parser-a running environment that allows JS to do something with the built-in objects and methods provided by the running environment.　　　　　　　　　　 For example, Fs/http built-in objects. --JavaScript running on the server

1 start with a small example of the actual point, feel the Nodejs

var http = require (' http '); Http.createserver (function  (request, response) {  Response.writehead ($, {' Content-type ': ' Text/plain '});  Response.End (' Hello world\n ');}). Listen (8888); Console.log (' Server running at http://127.0.0.1:8888/');

This creates an HTTP server. On the http://127.0.0.1:8888, you can see the output of Hello World with a browser access.

2 Modules

Require// reference module　

Referencing other modules in Main.js

var hello=require ('./hello.js ');

Exports// export object to the module used for require module

exports.hello=function() {console.log (' Hello World ');}

function hello () {console.log (' Hello World ');} Exports.hello=hello;

Module//Can access information for the current module, primarily for replacing the default export object of the module

Note: The code in the module is only executed once at initialization time, and calls cache reuse when reused

When there are multiple modules in a package, the main module can be named Index.js, or Package.json, through the directory as the access to the package (not the file path);

package.json{  "name": the folder where the current folder of the "package"/  / module is located  //  / Home/node/package/lib/xx.js}// Access Module require ('/home/node/package ')  ha, A look is the feeling of visiting the package

4 NPM

Get third-party packages

Download Third Party package NPM install AGRV;

or configure it in the Package.json.

{    "name": "Node-echo",    "main": "./lib/echo.js",    "dependencies": {         "argv": "0.0.2"    }}

5 Formal little copy of the small file

var // built-in file templates function Copy (SRC,DST) {  fs.writefilesync (Dst,readfilesync (SRC)}function  Main (argv) {      copy (argv[0],argv[1]);} Main (process.argv.slice[2]);//argv[0],argv[2] The absolute path of the executing program and the master module stored separately

These small files belong to one-time write memory, read out at once, will cause memory explosion

Write large files (flow-through)

var fs = require (' FS '); function copy (src, DST) {    fs.createreadstream (SRC). Pipe (Fs.createwritestream (DST)); (read side write)}  function  Main (argv) {    copy (argv[0], argv[1]);} Main (Process.argv.slice (2));

6 Event object, Eventemitter time emission and event monitoring function encapsulation

Each event has an event name (string) and several parameters, and an event can have multiple event supervisors

var events = require (' Events 'varnew  events. Eventemitter (); Emitter.on (function(arg1, arg2) {//Register event Listener    console.log (' first event ', Arg1, arg2);}); Emitter.on (function(arg1, arg2) {     console.log (' second event ', Arg1, arg2);}); Emitter.emit (' someevent ', ' Byvoid ', 1991); Launch event, call event listener in turn

Eventemitter API:

Eventemitter.on (Event,listener);

Eventemitter.once (Event,listener); event is only released once

Eventemitter.removelistener (event,listener); removing events

Error is a special event for Eventemitter

Encountered exception is the launch Error event, call the listener function, to avoid the program crashes

var events = require (' Events 'var emitter = newevents. Eventemitter (); Emitter.on (' error ',function() {   console.log (' Error ')}) Emitter.emit (

About inheritance: Most of the time we don't use eventemitter directly, but inherit it from the object. Including FS, NET, HTTP, as long as the core modules that support event response are Eventemitter subclasses.

7 Global Variables

Process

PROCESS.ARGV command line parameter array

Process.stdout/process.stdin

Process.stdin.resume (); Process.stdin.on (function(data) {Process.stdout.write (' Read From console: ' +

Process.nexttick (callback), set the task for the time cycle, the next loop response thing call callback, the complex work split into small time, improve response speed, save response time (I understand this is not very good)

(Write these today, then go on to write them later)

A shallow understanding of node. js