TS2345: Argument is not assignable - in CI

By Kaveh Alemi·Latchkey

You passed an argument whose type does not match the parameter a function expects.

What this error means

Type-checking fails with TS2345 at a call site, naming the argument type and the expected parameter type.

src/cart.ts(18,14): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.

Common causes

How to fix it

Make the argument match the parameter

1. Convert or narrow the value before the call
2. Avoid as casts that silence the error without fixing it

addToCart(Number(productId))

Fix the signature if the type is too narrow

1. Widen the parameter type deliberately (e.g. string | number)
2. Update calls to a dependency's new shape

How to prevent it

• Run tsc --noEmit in CI, enable strict, and convert at boundaries instead of casting.

Frequently asked questions

Related guides

References

• Node.js documentation
• npm CLI documentation
• GitHub Actions documentation