TIL how to append a date to a filename in Node

POSTED ON: Feb 01, 2022

TAGS: node filename

My goal was to create a helper function that allows me to build a new file, and append a date to a filename for logging.

So:

// BEFORE
filename.js

// AFTER
filename-1644470506946.js

That string of numbers? 1644470506946 is the timestamp in Unix, which you can find the conversion here: https://www.unixtimestamp.com/

But also, it should keep the directory path.

What I came up with: #

function generateFile(src, data, setDate = true) {
  const date = Date.now();

  // check if there's a slash in it
  const directoryOnly = src.substr(0, src.lastIndexOf("/"));
  const filenameOnly = src.substring(src.lastIndexOf("/") + 1);

  // modify filename with date
  let fileName = setDate
    ? `${filenameOnly.split(".")[0]}-${date}.${filenameOnly.split(".")[1]}`
    : filenameOnly;

  fs.writeFileSync(`${directoryOnly}/${fileName}`, data, (err) => {
    if (err) {
      console.error(err);
      return;
    }
  });
}

To use it:

generateFile('./public/data-backup.json',  JSON.stringify(result)); // /public/data-backup-1644470506946.json
generateFile('./public/data.json',  JSON.stringify(result), false); // /public/data.json
generateFile('./data.json',  JSON.stringify(result), true); // data-1644470506946.json

Future improvements #

Consider using path? https://nodejs.org/api/path.html

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