A brief analysis of the http module and export sharing in Nodejs

This article talks about the basics of node, the understanding and cases of http module and module.exports export sharing, I hope it will be helpful to everyone!

1. http module

The http module is a module officially provided by Node.js for creating web servers. [Related tutorial recommendations: nodejs video tutorial]

Through the http.createServer() method provided by the http module, you can easily turn an ordinary computer into a web server , thereby providing web resource services to the outside world.

1. Create a web server

• Import the http module
• Create a web server instance
• Bind to the server instance request event, listen to the client's request
• Start the server

Example: Listen to the 8080 service

// 导入 http 模块
const http = require('http')
// 创建 web 服务器实例
const server = http.createServer()
// 为服务器实例绑定 request 事件 监听客户端的请求
server.on('request', function (req, res) {
    console.log('请求中...')
})
// 启动服务
server.listen(8080, function () {
    console.log('http://127.0.0.1:8080')
})

2. req request object

As long as the server receives the client's request, it will call the request event processing function bound to the server through server.on()

Example: In the event handling function, access data or attributes related to the client

// 导入 http 模块
const http = require('http')
// 创建 web 服务器实例
const server = http.createServer()
// req 是请求对象 包含了与客户端相关的数据和属性
server.on('request', (req) => {
    // req.url 客户端请求的 url 地址
    const url = req.url
    // req.method 是客户端请求的 method 类型
    const method = req.method
    const str = `Your request url is ${url} and request method is ${method}`
    console.log(str)
})
// 启动服务
server.listen(8080, function () {
    console.log('http://127.0.0.1:8080')
})

3. res response object

In the server's request event handling function, if you want to access server-related data or properties, you need to use response

Example: Request response

// 导入 http 模块
const http = require('http')
// 创建 web 服务器实例
const server = http.createServer()
// req 是请求对象 包含了与客户端相关的数据和属性
server.on('request', (req, res) => {
    // req.url 客户端请求的 url 地址
    const url = req.url
    // req.method 是客户端请求的 method 类型
    const method = req.method
    const str = `Your request url is ${url} and request method is ${method}`
    console.log(str)
    // 调用 res.end() 方法 向客户端响应一些内容
    res.end(str)
})
// 启动服务
server.listen(8080, function () {
    console.log('http://127.0.0.1:8080')
})

4. Solve the problem of Chinese garbled characters

When calling the res.end() method, report to the client When sending Chinese content, garbled characters will occur, and you need to manually set the encoding format of the content

Example: Solve Chinese garbled characters

// 导入 http 模块
const http = require('http')
// 创建 web 服务器实例
const server = http.createServer()
// req 是请求对象 包含了与客户端相关的数据和属性
server.on('request', (req, res) => {
    // req.url 客户端请求的 url 地址
    const url = req.url
    // req.method 是客户端请求的 method 类型
    const method = req.method
    const str = `请求地址是 ${url} 请求方法是 ${method}`
    console.log(str)
    // 设置 Content-Type 响应头 解决中文乱码问题
    res.setHeader('Content-Type', 'text/html; charset=utf-8')
    // 调用 res.end() 方法 向客户端响应一些内容
    res.end(str)
})
// 启动服务
server.listen(8080, function () {
    console.log('http://127.0.0.1:8080')
})

5. Respond to different html content according to different URLs

Example: The steps are as follows

• Get the requested url address
• Set the default response content to 404 Not found
• Determine whether the user requested / or /index.html home page
• Determine whether the user requested Whether to set the Content-Type response header for /about.html About page
• to prevent Chinese garbled characters
• Use res.end() to respond the content to the client

// 导入 http 模块
const http = require('http')
// 创建 web 服务器实例
const server = http.createServer()
// req 是请求对象 包含了与客户端相关的数据和属性
server.on('request', (req, res) => {
    // req.url 客户端请求的 url 地址
    const url = req.url
    // 设置默认的内容为 404 Not Found
    let content = &#39;<h1>404 Not Found!</h1>&#39;
    // 用户请求页是首页
    if(url === &#39;/&#39; || url === &#39;/index.html&#39;) {
        content = &#39;<h1>首页</h1>&#39;
    } else if (url === &#39;/about.html&#39;) {
        content = &#39;<h1>关于页面</h1>&#39;
    }
    // 设置 Content-Type 响应头 防止中文乱码
    res.setHeader(&#39;Content-Type&#39;, &#39;text/html; charset=utf-8&#39;)
    // 调用 res.end() 方法 向客户端响应一些内容
    res.end(content)
})
// 启动服务
server.listen(8080, function () {
    console.log(&#39;http://127.0.0.1:8080&#39;)
})

## 2. Module classification in Node.js

1. Three major module categories

Built-in modules: Officially provided by node.js, such as fs, path, http, etc.
• Custom module: Every .js file created by the user is a custom module
• Third-party module: A module developed by a third party, which must be downloaded before use

2. Module scope

Prevents the problem of global variable pollution

Example:

index.js file

const username = '张三'

function say() {
    console.log(username);
}

test.js file

const custom = require('./index')

console.log(custom)

##3. module.exports object In a custom module, you can use the module.exports object to

share members within the module

for external use. When the external require() method imports a custom module, what is obtained is the object pointed to by module.exports

Example:

index.js file

const blog = '前端杂货铺'

// 向 module.exports 对象上挂载属性
module.exports.username = '李四'
// 向 module.exports 对象上挂载方法
module.exports.sayHello = function () {
    console.log('Hello!')
}
module.exports.blog = blog

test.js file

const m = require('./index')

console.log(m)

4、共享成员时的注意点

使用 require() 方法导入模块时，导入的结果，永远以 module.exports 指向的对象为准

示例：

index.js 文件

module.exports.username = '李四'

module.exports.sayHello = function () {
    console.log('Hello!')
}

// 让 module.exports 指向一个新对象
module.exports = {
    nickname: '张三',
    sayHi() {
        console.log('Hi!')
    }
}

test.js 文件

const m = require('./index')

console.log(m)

5、exports 和 module.exports

默认情况下，exports 和 module.exports 指向同一个对象。

最终共享的结果，还是以 module.exports 指向的对象为准。

示例：

index1.js 文件

exports.username = '杂货铺'

module.exports = {
    name: '前端杂货铺',
    age: 21
}

index2.js 文件

module.exports.username = 'zs'

exports = {
    gender: '男',
    age: 22
}

index3.js 文件

exports.username = '杂货铺'

module.exports.age = 21

index4.js 文件

exports = {
    gender: '男',
    age: 21
}

module.exports = exports

module.exports.username = 'zs'

对 index2.js 文件结果的解析如下：

对 index4.js 文件结果的解析如下：

注意：为防止混乱，尽量不要在同一个模块中同时使用 exports 和 module.exports

更多node相关知识，请访问：nodejs 教程！

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