Suppose you have many folders named with a number prefix:

1-yo
2-hey
3-cool
4-hi
5-whatsup

You need to insert a new folder in the middle and renumber the rest:

1-yo
2-hey
3-NEWONE
3-cool
4-hi
5-whatsup

You want to increment the numbers of all folders that come after the new one:

1-yo
2-hey
3-NEWONE
4-cool
5-hi
6-whatsup

You can automate this with a Node.js script. For example, save the script as increment.js and pass the starting number as a command-line argument:

node increment.js 4

Read the number from process.argv:

const args = process.argv.slice(2)
const startingNumber = args[0]

If no number is provided, show an error and exit:

if (!startingNumber) {
  console.log('Add a number argument')
  return
}

Run the script from the folder that contains the numbered subfolders. List the contents of the current folder:

const fs = require('fs')

const folders = fs
  .readdirSync('./')
  .map(fileName => {
    return fileName
  })

Filter to keep only folders:

const fs = require('fs')

const isFolder = fileName => {
  return !fs.lstatSync(fileName).isFile()
}

const folders = fs
  .readdirSync('./')
  .map(fileName => {
    return fileName
  })
  .filter(isFolder)

Iterate over the folders:

folders.map(folder => {

})

Extract the number from each folder name:

folders.map(folder => {
  const result = folder.match(/(\d)+/)
})

If the name contains a number, parse it:

folders.map(folder => {
  const result = folder.match(/(\d)+/)
  if (result !== null) {
    const num = parseInt(result[0])
  }
})

If the folder number is greater than or equal to the starting number, rename it with the incremented number:

folders.map(folder => {
  const result = folder.match(/(\d)+/)
  if (result !== null) {
    const num = parseInt(result[0])
    if (num >= startingNumber) {
      fs.renameSync(folder, folder.split(num).join(num + 1))
    }
  }
})

Full script:

const fs = require('fs')

const args = process.argv.slice(2)
const startingNumber = args[0]
if (!startingNumber) {
  console.log('Add a number argument')
  return
}

const isFolder = fileName => {
  return !fs.lstatSync(fileName).isFile()
}

const folders = fs
  .readdirSync('./')
  .map(fileName => {
    return fileName
  })
  .filter(isFolder)

folders.map(folder => {
  const result = folder.match(/(\d)+/)
  if (result !== null) {
    const num = parseInt(result[0])
    if (num >= startingNumber) {
      fs.renameSync(folder, folder.split(num).join(num + 1))
    }
  }
})

Lessons in this unit:

0:	Introduction
1:	How to check if a file exists in Node.js
2:	How to create an empty file in Node.js
3:	How to get the names of all the files in a folder in Node
4:	How to get the last updated date of a file using Node.js
5:	How to remove a file with Node.js
6:	How to write a JSON object to file in Node.js
7:	How to empty a folder in Node.js
8:	Working with file descriptors in Node
9:	Node File Paths
10:	Node file stats
11:	Working with folders in Node
12:	How to use the Node.js fs module with async/await
13:	How to get the current folder in Node
14:	How to get the file extension in Node.js from the MIME type
15:	How to get the file extension in Node.js
16:	How to list files in a folder in Node
17:	How to mass rename files in Node.js
18:	Node.js get all files in a folder recursively
19:	▶︎ Incrementing multiple folders numbers at once using Node.js
20:	Save some text to a file in Node.js