How to bulk convert file names using Node.js

You can bulk convert file names with a short Node.js script: find the files with a glob pattern, compute the new name for each one, then copy or rename them with the fs module.

Here’s the real case where I needed this. I had to convert my folders structure from something like this:

• posts/test/index.md
• posts/hey-cool-post/index.md

to this:

• posts/test.md
• posts/hey-cool-post.md

removing the folder that contains an index.md file, and instead have the markdown file itself have the post slug (the part that’s used as the post URL).

I had hundreds of posts, so renaming by hand was not an option.

I used a Node.js script to do this. The script relies on a glob pattern to find the files — you can test patterns like this in my glob pattern tester.

Install glob first:

npm install glob

Here it is:

import fs from 'fs/promises'
import { glob } from 'glob'

const root_folder = '.' //search in the current folder

const files = await glob(root_folder + '/**/index.md')

for (const file_path of files) {
  const match = file_path.match(/\/(.*?)\//)
  const folder_name = match[1]

  try {
    await fs.copyFile(file_path, './' + folder_name + '.md')
    console.log('File moved!')
  } catch (err) {
    console.log('Error Found:', err)
  }
}

How the script works

The './**/index.md' pattern matches every index.md file, at any depth, starting from the current folder. glob returns a promise with the list of matching paths.

For each path, the regular expression /\/(.*?)\// captures the text between the first two slashes. For ./hey-cool-post/index.md that’s hey-cool-post, the folder name I want to use as the file name.

Then fs.copyFile() copies index.md to a new file named after its folder, in the current directory.

One thing to watch out for

fs.copyFile() copies, it doesn’t move. The original index.md files and their folders are still there after the script runs. I liked that, because I could check the result before deleting anything. Once you’ve verified the new files, remove the old folders. And run this kind of script on a folder tracked by Git, so a wrong result is one checkout away from being undone.

Want me to talk about your product? You can sponsor this site.