Type unknown TypeScript TS18046

Why This Happens

In TypeScript, you need to narrow an unknown type before using it. This is one of the most common TypeScript errors developers encounter. Understanding the root cause helps you fix it quickly and prevent it from recurring.

The Problem

function handle(err: unknown) {
  console.log(err.message);
}

The Fix

function handle(err: unknown) {
  if (err instanceof Error)
    console.log(err.message);
}

Step-by-Step Fix

1. 1

   Identify the error

   Look at the error message: TS18046: 'x' is of type 'unknown'. This tells you exactly what went wrong.

2. 2

   Find the cause

   Check the stack trace to find which line of your TypeScript code triggered this error.

3. 3

   Apply the fix

   Use the corrected code pattern shown above. Test to confirm the error is resolved.