如何操作 Node.js 中带有承诺的基于回调的 fs.rename()方法？
原文:https://www . geesforgeks . org/操作方法-基于回调-fs-rename-method-with-promises-in-node-js/
fs.rename() 方法是在 Node.js 的文件系统模块中定义的，文件系统模块基本上就是和用户电脑的硬盘进行交互。rename()方法用于将给定旧路径上的文件重命名为给定新路径。如果新路径文件已经存在，它将被覆盖，如果在新路径上存在一个目录，则会发生错误。
fs.rename()方法基于回调。使用回调方法导致回调嵌套或回调地狱问题的可能性很大。因此，为了避免这种情况，我们几乎总是喜欢使用基于承诺的方法。使用一些额外的 node.js 方法，我们可以用 promise 方式操作一个基于回调的方法。
语法:
fs.rename(oldPath, newPath)
注意:如果用承诺的方式操作，不需要回调。
参数:该方法接受两个参数，如上所述，如下所述:
- oldpath: 它是一个字符串、缓冲区或网址，用于指定必须重命名的文件的路径。
- newpath: 它是一个字符串、缓冲区或网址，指定旧文件要替换的文件的路径。
方法:基于回调的 fs.rename()方法。为了用承诺来操作它，首先，我们使用在 utilities 模块中定义的 promisify()方法将其转换为基于承诺的方法。
示例 1: 文件名:index.js
// Importing File System and Utilities module
const fs = require('fs')
const util = require('util')
// Convert callback based methods to promise
// based methods
const readDir = util.promisify(fs.readdir)
const rename = util.promisify(fs.rename)
readDir(process.cwd())
.then(files => {
console.log(`Contents before rename operation: `)
// Contents of the current directory
for(let file of files) {
console.log(file)
}
console.log('\nAttempt to rename file : \n')
// Rename operation
return rename('test.txt', 'testFile.txt')
})
.then(() => {
// The process.cwd() gives current working
// directory
return readDir(process.cwd())
})
.then(files => {
console.log(`Contents after rename operation: `)
// Contents of the current directory
for(let file of files) {
console.log(file)
}
})
.catch(err => {
console.log(`Error occurs,
Error code -> ${err.code},
Error No -> ${err.errno}`);
})
使用异步等待实现相同的功能。
// Importing File System and Utilities module
const fs = require('fs')
const util = require('util')
// Convert callback based methods to promise
// based methods
const readDir = util.promisify(fs.readdir)
const rename = util.promisify(fs.rename)
const renameOperation = async (oldpath, newpath) => {
console.log(`Contents before rename operation: `)
// Fetching contents of the directory before
// rename operation. The process.cwd() gives
// current working directory
const oldFiles = await
fs.promises.readdir(process.cwd())
// Contents of the current working directory
for(let file of oldFiles){
console.log(file)
}
console.log('\nAttempt to rename file : \n')
// Rename operation
await fs.promises.rename(oldpath, newpath)
console.log(`Contents after rename operation: `)
// Fetching contents of directory before
// rename operation
const newFiles = await
fs.promises.readdir(process.cwd())
// Contents of the current working directory
for(let file of newFiles) {
console.log(file)
}
}
renameOperation('test.txt', 'testFile.txt')
.catch(err => {
console.log(`Error occurs, Error code -> ${err.code},
Error No -> ${err.errno}`);
});
使用以下命令运行 index.js 文件:
node index.js
运行程序前的目录结构:
运行程序后的目录结构:
输出:
示例 2: 给定时，newpath 不是文件的路径，而是目录。 T3】文件名:index.js
// Importing File System and Utilities module
const fs = require('fs')
const util = require('util')
// Convert callback based methods to promise
// based methods
const readDir = util.promisify(fs.readdir)
const rename = util.promisify(fs.rename)
readDir(process.cwd())
.then(files => {
console.log(`Contents before rename operation: `)
// Contents of the current directory
for(let file of files) {
console.log(file)
}
console.log('\nAttempt to rename file : \n')
// Rename operation
return rename('testFile.txt', 'test')
})
.then(() => {
// The process.cwd() gives current
// working directory
return readDir(process.cwd())
})
.then(files => {
console.log(`Contents after rename operation: `)
// Contents of the current directory
for(let file of files) {
console.log(file)
}
})
.catch(err => {
console.log(`Error occurs,
Error code -> ${err.code},
Error No -> ${err.errno}`);
})
用异步等待实现相同的功能。
// Importing File System and Utilities module
const fs = require('fs')
const util = require('util')
// Convert callback based methods to promise
// based methods
const readDir = util.promisify(fs.readdir)
const rename = util.promisify(fs.rename)
const renameOperation = async (oldpath, newpath) => {
console.log(`Contents before rename operation: `)
// Fetching contents of directory before
// rename operation. The process.cwd()
// gives current working directory
const oldFiles = await readDir(process.cwd())
// Contents of the current working directory
for(let file of oldFiles) {
console.log(file)
}
console.log('\nAttempt to rename file : \n')
// Rename operation
await rename(oldpath, newpath)
console.log(`Contents after rename operation: `)
// Fetching contents of directory before rename operation
const newFiles = await readDir(process.cwd())
// Contents of the current working directory
for(let file of newFiles) {
console.log(file)
}
}
renameOperation('testFile.txt', 'test')
.catch(err => {
console.log(`Error occurs,
Error code -> ${err.code},
Error No -> ${err.errno}`);
});
使用以下命令运行 index.js 文件:
node index.js
输出:
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