ERR_INVALID_ARG_TYPE 🟩 Node.js

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received undefined

A Node API got an argument of the wrong type — usually undefined because an env var or config value is missing.

Seen on: Node.js

Meaning

The message names the argument and what was received. "Received undefined" almost always means a missing environment variable or a misspelled option.

Common causes

  • process.env.X undefined (missing .env value)
  • Passing an object/number where a string is expected
  • Old tool calling a newer Node API differently

⚡ Quick fix

  1. Validate required env vars at startup
  2. Log the value before the call
  3. Upgrade the tool that calls the API

Detailed fix by platform

Node.js

  1. javascript
    const dir = process.env.UPLOAD_DIR;
if (!dir) throw new Error('UPLOAD_DIR is not set');

How to diagnose

  1. Argument — Which argument and received type?
  2. Source — Where does it come from?

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