node.js基础内容

1 var fs = require(‘fs‘);
2 
3 fs.readFile(‘text.txt‘,function(err,data){
4     if(err) return console.log(err);
5     console.log(data.toString());
6 })
7 console.log("end!!");

 1 // 声明需要事件
 2 var events = require(‘events‘);
 3 // 创建事件对象
 4 var eventEmitter = new events.EventEmitter();
 5 // 声明触发事件执行的函数
 6 var connected = function connected() {
 7     console.log(‘connection succesful!‘)
 8     eventEmitter.emit(‘data_received.‘);
 9 }
10 // 绑定事件
11 eventEmitter.on("connection",connected);
12 eventEmitter.on("data_received",function(){
13     console.log(‘data received succesfully.‘);
14 });
15 // 事件触发
16 eventEmitter.emit(‘connection‘);
17 console.log(‘code end!‘);

 1 var fs = require("fs");
 2 
 3 fs.readFile(‘test.txt‘, function (err, data) {
 4     if (err){
 5        console.log(err.stack);
 6        return;
 7     }
 8     console.log(data.toString());
 9 });
10 console.log("Program Ended");

 1 // 需要事件
 2 var events = require(‘events‘); 
 3 // 创建事件对象
 4 var eventEmitter = new events.EventEmitter();
 5 // 事件1
 6 var listner1 = function listner1() {
 7     console.log(‘this is 11111‘);
 8 }
 9 // 事件2
10 var listner2 = function listner2() {
11     console.log(‘this is 22222‘);
12 }
13 // 事件监听addListener与on效果相同
14 eventEmitter.addListener(‘connection‘,listner1);
15 eventEmitter.on(‘connection‘,listner2);
16 // 另一种写法
17 var eventListeners = require(‘events‘).EventEmitter.listenerCount(eventEmitter,‘connection‘);
18 console.log(eventListeners + " Listner(s) listening to connection event");
19 // 触发事件
20 eventEmitter.emit(‘connection‘);
21 // 移除事件监听
22 eventEmitter.removeListener(‘connection‘, listner1);
23 console.log("Listner111 will not listen now. removeListener");
24 // 再触发事件
25 eventEmitter.emit(‘connection‘);
26 // 添加事件监听
27 eventListeners = require(‘events‘).EventEmitter.listenerCount(eventEmitter,‘connection‘);
28 console.log(eventListeners + " Listner(s) listening to connection event");
29 
30 console.log("Program Ended.");

 1 var buffer = new Buffer(26);
 2 console.log("buffer length: " + buffer.length);
 3 var data = "YiiBai.com";
 4 
 5 buffer.write(data);
 6 console.log(data + ": " + data.length + " characters, " + Buffer.byteLength(data, ‘utf8‘) + " bytes");
 7 
 8 var buffer1 = buffer.slice(0,14);
 9 console.log("buffer1 length: " + buffer1.length);
10 console.log("buffer1 content: " + buffer1.toString());
11 
12 for (var i = 0 ; i < 26 ; i++) {
13     buffer[i] = i + 97; // 97 is ASCII a
14   }
15   console.log("buffer content: " + buffer.toString(‘ascii‘));
16   
17   var buffer2 = new Buffer(4);
18 
19   buffer2[0] = 0x3;
20   buffer2[1] = 0x4;
21   buffer2[2] = 0x23;
22   buffer2[3] = 0x42;
23 
24 //reading from buffer
25 console.log(buffer2.readUInt16BE(0));
26 console.log(buffer2.readUInt16LE(0));
27 console.log(buffer2.readUInt16BE(1));
28 console.log(buffer2.readUInt16LE(1));
29 console.log(buffer2.readUInt16BE(2));
30 console.log(buffer2.readUInt16LE(2));
31 
32 var buffer3 = new Buffer(4);
33 buffer3.writeUInt16BE(0xdead, 0);
34 buffer3.writeUInt16BE(0xbeef, 2);
35 console.log(buffer3);
36 
37 buffer3.writeUInt16LE(0xdead, 0);
38 buffer3.writeUInt16LE(0xbeef, 2);
39 
40 console.log(buffer3);
41 
42 //convert to a JSON Object
43 var json = buffer3.toJSON();
44 console.log("JSON Representation : ");
45 console.log(json);
46 
47 //Get a buffer from JSON Object
48 var buffer6 = new Buffer(json);
49 console.log(buffer6);
50 
51 //copy a buffer
52 var buffer4 = new Buffer(26);
53 buffer.copy(buffer4);
54 console.log("buffer4 content: " + buffer4.toString());
55 
56 //concatenate a buffer
57 var buffer5 = Buffer.concat([buffer,buffer4]);
58 console.log("buffer5 content: " + buffer5.toString());

 1 var fs = require("fs");
 2 var data = ‘‘;
 3 //create a readable stream
 4 var readerStream = fs.createReadStream(‘text.txt‘);
 5 
 6 //set the encoding to be utf8. 
 7 readerStream.setEncoding(‘UTF8‘);
 8 
 9 //handle stream events
10 readerStream.on(‘data‘, function(chunk) {
11    data += chunk;
12 });
13 
14 readerStream.on(‘end‘,function(){
15    console.log(data);
16 });
17 
18 readerStream.on(‘error‘, function(err){
19    console.log(err.stack);
20 });
21 console.log("-------------Program Ended---------------");

 1 var fs = require("fs");
 2 var data = ‘Yiibai.Com‘;
 3 //create a writable stream
 4 var writerStream = fs.createWriteStream(‘text1.txt‘);
 5 
 6 //write the data to stream
 7 //set the encoding to be utf8. 
 8 writerStream.write(data,‘UTF8‘);
 9 
10 //mark the end of file
11 writerStream.end();
12 
13 //handle stream events
14 writerStream.on(‘finish‘, function() {
15     console.log("Write completed.");
16 });
17 
18 writerStream.on(‘error‘, function(err){
19    console.log(err.stack);
20 });
21 console.log("--------------Program Ended---------------");

 1 var util = require(‘util‘);
 2 
 3 //printing to console
 4 process.stdout.write("Hello World!" + "\n");
 5 
 6 //reading passed parameter
 7 process.argv.forEach(function(val, index, array) {
 8    console.log(index + ‘: ‘ + val);
 9 });
10 
11 //executable path
12 console.log(process.execPath);
13 
14 //print the current directory
15 console.log(‘Current directory: ‘ + process.cwd());
16     
17 //print the process version
18 console.log(‘Current version: ‘ + process.version);
19 
20 //print the memory usage
21 console.log(util.inspect(process.memoryUsage()));