Get file type using fs/node.js

Question

I have a folder with few files and I need to get type/extension of the file matching with the number I generate in my num variable, so is there any way I can do it?

My current code is:

fs.readdir(dir, (err, files) => {
  const num = (Math.floor(Math.random() * files.length) + 1).toString();
  // here I need to get file type/extension
}

files variable return this: ['1.jpg', '2.png', '3.gif']

Answer 1

To find a file in a list of files regardless of the extension, use path.basename and path.extname on the files in the list to chop the extensions. For a single search, use files.find() .

const filename = files.find(x => path.basename(x, path.extname(x)) === num.toString()))

However, for random selection purposes, it may be better to simply take a random entry from files . The reason is, if the files are all sequentially numbered it's the same thing, but if they aren't all sequentially numbered the above can break.

const filename = files[num] // and take away + 1 from num

Answer 2

Instead of matching the whole file name, You can just generate a random number in ArrayList and get that file.

const fs = require("fs");
const path = require("path");

fs.readdir(__dirname, (err, files) => {
  const randomNum = Math.floor(Math.random() * files.length);
  // get the random file
  let randomFileName = files[randomNum];
  console.log(randomFileName);

  /// Get unique exts
  const exts = [...new Set(files.map((name) => path.extname(name)))];
  console.log(exts);
  const randomExt = Math.floor(Math.random() * exts.length);
  
  // Get file with random ext
  randomFileName = files.find((x) => path.extname(x) === exts[randomExt]);
  console.log(randomFileName);
});