NodeJS: How to decode base64 encoded string back to binary?

I was implementing password hashing with salt, so I generated salt as binary, hashed the password, base64 encoded the password and salt then stored them into database.

Now when I am checking password, I am supposed to decode the salt back into binary data, use it to hash the supplied password, base64 encode the result and check if the result matches the one in database.

The problem is, I cannot find a method to decode the salt back into binary data. I encoded them using the Buffer.toString method but there doesn't seem to be reverse function.