nodejs

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inherits: 继承   chunk: 片段    pipe: 管道

require: 引入   request: 请求    response: 响应    listen: 监听

text/plain: 文本/纯   encode: 编码

var events = require('events');  //核心事件库
var util = require('util')  //核心工具库
var fs = require('fs');  //文件系统库
var http = require('http');   //http模块
var url = require('url');     //url工具库
var querystring = require('querystring');

var express = require('express');

　

console.dir(req.params);  //输出一个对象包含的内容

　　

序列化（JSON.stringify(Obj)）  对象→string

反序列化（JSON.parse(objString)）   string→对象

var Obj = {
        name: 'sunjia',
        job: 'programmer',
        age: 37
    };

console.log(Obj);
//{name: "sunjia", job: "programmer", age: 37}    //对象

console.log(JSON.stringify(Obj));
//"{"name":"sunjia","job":"programmer","age":37}"    //字符中（对象形式的），便于传输

console.log(JSON.parse('{"name":"sunjia","job":"programmer","age":37}'));
console.log(JSON.parse(JSON.stringify(Obj)));
//{name: "sunjia", job: "programmer", age: 37}  //对象

　　

　

fs异步: fs.readFile()、fs.writeFile()

//同步：sync

var fs = require('fs');

var readMe = fs.readFileSync("readMe.txt","utf8");

console.log(readMe);
console.log("finished");

// you read me!
// finished

// 异步方法都要加回调函数

var fs = require('fs');

var readMe = fs.readFile("readMe.txt","utf8", function(err,data) {
    console.log(data);
});

console.log("finished");


// finished
// you read me!

　

node事件

var events = require('events'); //引入核心事件库

var myEmitter = new events.EventEmitter();  //新建（实例化）一个事件对象

myEmitter.on('someEvent', function(message) {  //监听事件
    console.log(message);
})

myEmitter.emit('someEvent', 'the event was emitted')//触发事件（根据事件名称）


// the event was emitted

　　

全局变量

// console.log(__dirname);
// console.log(__filename);

// require exports

// console.log("hello world");
// setTimeout(() => {
//     console.log('2 秒开始执行')
// }, 2000);


// var time = 0;
// var timer = setInterval(function() {
//     time += 2;
//     console.log(time + " seconds have passed");
//     if(time > 5) {
//         clearInterval(timer)
//     }
// }, 2000);

同一个变量：后边的值覆盖前边的值

var pi = 3.14;

var adder = function(a) {
    return `the sum of 2 number is ${a+pi}`;
}

var pi = 1;

console.log(adder(1));

// the sum of 2 number is 2

var pi = 3.14;

var adder = function(a) {
    return `the sum of 2 number is ${a+pi}`;
}

var pi = 1;

console.log(adder("1"));

// the sum of 2 number is 11