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Node.js Tips & Tricks

Node.js documentation​

Display objects​

To display all the members of an object, use:

const util = require('util')
console.log(util.inspect(something))

Check if file/folder exist​

Use stat().

    try {
      await fsPromises.stat(aPath)
      // It does.
    } catch (err) {
      // It does not.
    }

Use lstat(), since stat() follows the link.

const stats = await fsPromises.lstat(aPath)

if (stats.isSymbolicLink()) {
  // ...
}

Iterate over a directory​

Use readdir() to return an array of file names or structures.

  static async chmodRecursive ({ inputPath, readOnly, log }) {
    assert(inputPath, 'Mandatory inputPath')
    assert(log, 'Mandatory log')

    const Self = this

    const stat = await fsPromises.lstat(inputPath)
    // log.trace(util.inspect(stat))

    // The order is important, process the folder before
    // changing it to RO.
    if (readOnly && stat.isDirectory()) {
      log.trace(inputPath)
      const files = await fsPromises.readdir(inputPath, { withFileTypes: true })
      for (const file of files) {
        await Self.chmodRecursive({
          inputPath: path.resolve(inputPath, file.name),
          readOnly,
          log
        })
      }
    }

    const mode = stat.mode
    // For RO, remove all W bits, for RW add only user.
    const newMode = readOnly
      ? mode & ~(fs.constants.S_IWUSR | fs.constants.S_IWGRP |
          fs.constants.S_IWOTH)
      : mode | (fs.constants.S_IWUSR)

    await fsPromises.chmod(inputPath, newMode)

    // If RW, process the folder after changing it to RW.
    if (!readOnly && stat.isDirectory()) {
      log.trace(inputPath)
      const files = await fsPromises.readdir(inputPath, { withFileTypes: true })
      for (const file of files) {
        await Self.chmodRecursive({
          inputPath: path.resolve(inputPath, file.name),
          readOnly,
          log
        })
      }
    }
  }