Let's talk about the commonly used file systems in Node.js

Node.js is a platform that can run JavaScript. It uses an event-driven, non-blocking I/O model to efficiently handle a large number of requests in a single-threaded environment, making it the preferred technology for modern web application development.

During the Node.js development process, writing high-quality comments is crucial in order to better read and maintain the code. This article introduces and annotates a large number of Node.js methods, hoping to help developers better understand and apply Node.js.

1. File System

fs.access(path[, mode], callback)

判断文件或目录是否存在，mode为文件操作权限，默认为fs.constants.F_OK。
callback传递一个可能出现的错误参数。

fs.appendFile(file, data [, options], callback)

将数据异步地添加到文件的尾部，options包括encoding，mode和flag，默认为UTF8编码。
callback传递一个可能出现的错误参数。

fs.chmod(path, mode, callback)

更改指定路径所指向的文件或目录的权限，mode为文件操作权限。
callback传递一个可能出现的错误参数。

2. Http (Hypertext Transfer Protocol)

http.createServer(options)

创建一个HTTP服务器对象，在接收到请求时调用requestListener函数进行响应。
options包括maxHeadersCount和timeout，默认为66666和2分钟，调用callback有request和response两个参数。

http.request(options[, callback])

发送一个HTTP请求，options中包括host、port、path和method等信息。
callback有一个参数为response对象。

http.response.writeHead(statusCode, statusMessage)

statusCode为HTTP响应状态码，statusMessage为HTTP响应状态消息，headers为HTTP响应头。
返回一个响应头。

3. Path(path)

path.basename(path[, ext])

返回文件路径的最后一部分，并删除文件扩展名ext。

path.dirname(path)

返回文件路径的目录名。

path.extname(path)

返回文件的扩展名。

path.join(path1[, ...])

将路径片段连接成一个路径。

4. Stream(stream)

stream.on(event, listener)

为指定事件添加一个监听器，事件有data、end、error、close等。

stream.pipe(destination[, options])

将可读流的数据写入可写流。

stream.readable

检查流是否可以读取。

stream.writable

检查流是否可以写入。

5. Events

events.EventEmitter.on(event, listener)

为指定事件添加一个监听器，事件有newListener和removeListener。

events.EventEmitter.emit(event, arg1[, ...])

发射事件。

events .EventEmitter.once(event, listener)

为指定事件添加一个一次性监听器，事件只能被调用一次后被移除。

Summary

In the development process of Node.js, appropriate annotations are very necessary. This article mainly introduces the file system, HTTP, path, stream, event and other methods commonly used in Node.js, and comments on each method. I hope this article can provide convenience for Node.js developers and better develop high-quality Node.js applications.

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