Understanding TypeScript’s Most Common Type Errors

Every developer runs into a problem: you write what seems like perfectly reasonable code, and TypeScript shows an error. The error is red, the tooltip is long, and the compiler isn’t letting you move on.

Good.

This is exactly where we level up. In this lesson, we’re going to get inside the mind of the TypeScript compiler. Understand what it’s telling us, why it’s panicking, and how we can respond intelligently without reaching for any.

Let’s get comfortable with the most common types of errors and learn how to turn them into learning opportunities.

“Type ‘X’ is not assignable to type ‘Y’”  

This is a typical TypeScript error and one you’ll see a lot. It means we tried to assign a value that doesn’t match the expected type.