A brief discussion on fs.mkdir and fs.rmdir in Nodejs file module

This article will take you through Nodejs file operations fs.mkdir and fs.rmdir. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

[Recommended study: "nodejs Tutorial"]

Fs.mkdir file directory is newly added

Case usage

• Added directories level by level will successfully print success

fs.mkdir("a", function (err) {
    // 当a不存在的时候直接创建 a/b会报错
 if (err) {
    console.log(err);
    return;
  }
  console.log("success...");//success
});

• Cross-level directories that do not exist An error occurred when adding a directory under the directory! ! , the built-in module of node itself does not support adding new directories under non-existing directories (this is what I want to do)

fs. Enhanced version of mkdir

Recursive version

Idea

• According to "/ "Carry out cutting to generate array cache

• index initial value = 1; perform slice(0, index) on the array corresponding to the path in sequence, intercept and join('/') into the path string currentPath

• fs.stat is used to describe the status of the file. If the file does not exist, an error occurs

• An error occurred the previous day and called fs.mkdir( currentPath, call yourself recursively);

• The file exists and call yourself

Code implementation

function mkdir(pathStr, cb) {
  let pathList = pathStr.split("/");
  // 递归调用fs.mkdir
  let index = 1;
  function make(err) {
    if (err) return cb(err);
    if (index === pathList.length + 1) return cb();
    //每次 调用要将上次的已经生成的文件名做下次的目标文件，
    // 所以 slice(0, index) 第二参数也要 累加
    //slice(0, index) 截取后join('/')  成字符串
    let currentPath = pathList.slice(0, index++).join("/");
    // console.log("pathList.slice(0,index)", pathList.slice(0, index));
    fs.stat(currentPath, function (err) {
      if (err) {
        fs.mkdir(currentPath, make);
        console.log({ currentPath });
        // 如果不存在，再创建  fs.mkdir(currentPath, make);
      } else {
        make();
      }
    });
  }
  make();
}

Test:

No error is reported at this time

mkdir("a/b/c/d", function (err) {
  if (err) console.log(err);
   console.log("success...");
});

Print effect

##for loop await version

Implementation ideas

• Use '/' as the basis to cut the path into the corresponding array, and traverse the array in a for loop

• existsSync() in the for loop uses a synchronous method to detect whether the directory exists.

If the directory exists, return true , if the directory does not exist, return false 3. fs.mkdir(currentPath) does not exist

Implementation code

const fs = require("fs").promises; //node11后可以直接.promises
const { existsSync } = require("fs");
async function mkdir(pathStr, cb) {
  let pathList = pathStr.split("/");
  for (let i = 1; i <= pathList.length; i++) {
    let currentPath = pathList.slice(0, i).join("/");
    if (!existsSync(currentPath)) {
      await fs.mkdir(currentPath);
    }
  }
}

The call will recursively call the tile then chain call

mkdir("a/b/c/d")
  .then(() => {
    console.log("创建成功");
  })
  .catch((err) => {
    console.log(err);
  });

Print effect

##fs.rmdir file directory deletion

Case usage

Delete fs.rmdir directly in directories with subdirectories

const fs = require("fs");
const path = require("path");
fs.rmdir("a", function (err) {
  console.log(err);//会报错
});

Use results (error report)

fs.rmdir enhanced version

Serial version

Thinking

fs.stat will return the specific information of the file: the status of the file Information, modification time, creation time, directory status; the second parameter in the callback of fs.stat is to obtain the file object, the object method: isFile, isDirectory

• ##isFile directly fs.unlink (dir, cb); Delete the current file

• isDirectory calls fs.readdir to return an array of subdirectories

• Map the subdirectory array Traverse & parent file name, child file name, splice path.join(dir, item))

• Recursively call yourself on the spliced ​​path array in turn

• Delete all subdirectories and then delete itself

• ##Code implementation

  function rmdir(dir, cb) {
    fs.stat(dir, function (err, statObj) {
      // 1:判断dir的文件信息 statObj 是目录还是 文件
      if (statObj.isDirectory()) {
        // 1.1 读取文件夹fs.readdir 回调函数 里可以拿到文件夹读取结果
        fs.readdir(dir, function (err, dirs) {
          //   遍历 文件夹中文件，path 拼接 父文件名称+ 子文件名称
          dirs = dirs.map((item) => path.join(dir, item));
          // 把目录里面 的拿出来，一个删除后 删除下一个
          let index = 0;
          function step() {
            // 将子文件都删除完后，删除自己
            if (index === dirs.length) return fs.rmdir(dir, cb);
            //删除第一个成功后 继续调用rmdir 删除下一个子文件，直到index===dirs.length 时 删除自己
            rmdir(dirs[index++], step);
          }
          step();
        });
      } else {
        // 1.2 dir是文件 直接删除 用fs.unlink
        fs.unlink(dir, cb);
      }
    });
  }

Test

rmdir("a", function () {
  console.log("删除成功");
});

Execution result

Parallel version

Code implementation

const fs = require("fs").promises;
const path = require("path");
async function rmdir(dir) {
  let statObj = await fs.stat(dir);
  if (statObj.isDirectory) {
    let dirs = await fs.readdir(dir);
    await Promise.all(dirs.map((item) => rmdir(path.join(dir, item))));
    await fs.rmdir(dir);
  } else {
    return fs.unlink(dir);
  }
}

Call

rmdir("a").then(() => {
  console.log("并行删除成功");
});

Execution result

The difference between parallel and serial

Serial is understood to mean that a single thread can only execute the next one after the previous execution is completed. Parallel, asynchronous execution, no dependencies on each other Then the latter will be more efficient than the former

The operating essence of the file directory

The essence of the file directory: it is tree-structured data

• The operation of the file directory is the operation of the tree structure data

• Leave a hole for writing next time

  Tree structure Understanding

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