“TypeError: `level` is not a function” when using LevelJS 8.0.0

Question

Currently, I am testing LevelDB as a key–value store for my Node.js projects, but I am having this issue: when I import Level and run the sample code from the website, leveljs.org, I get this error:

TypeError: level is not a function
    at Object.<anonymous> (/home/runner/level/index.js:2:12)
    at Module._compile (node:internal/modules/cjs/loader:1155:14)

I have searched for this error and nothing has came up. I have tried importing Level in different ways and none of them have worked. Here is my code, which is identical to the sample code on the website:

const level = require('level')
const db = level('./db', { valueEncoding: 'json' })

db.put('key', { example: true }, function (err) {
  if (err) throw err

  db.get('key', function (err, value) {
    if (err) throw err
    console.log(value)
  })
})

Answer 1

When in doubt, always check the documentation at GitHub:

const { Level } = require('level')

// Create a database
const db = new Level('example', { valueEncoding: 'json' })

The README also has this note:

If you are upgrading: please see UPGRADING.md.

Version 8.0.0 (released 2022-03-25) states:

Changes to initialization

We started using classes, which means using new is now required. If you previously did:

const level = require('level')
const db = level('db')

You must now do:

const { Level } = require('level')
const db = new Level('db')

It also notes:

This release replaces leveldown and level-js with classic-level and browser-level.

The changelog lists this as a breaking change:

Breaking: switch to classic-level and browser-level (#215) (ad22b21) (Vincent Weevers).

The website is outdated (as of 2022-12-22, 22:09:03 UTC), and below the code sample it says:

As of level@5, the above code works in Node.js, Electron and browsers!

But you’re almost certainly using 8.0.0, not 5.0.0.

Shortly after bringing it up on the repository for leveljs.org, they fixed it.