TS18048: Value is possibly undefined - in CI

By Daniel Zoghalchali·Latchkey

A named value that can be undefined was used without first checking it.

What this error means

Type-checking fails with TS18048 naming an optional property or indexed access used unguarded.

src/cfg.ts(5,3): error TS18048: 'opts.timeout' is possibly 'undefined'.

Common causes

How to fix it

Default or guard the value

1. Provide a default with ?? or guard with a check

const timeout = opts.timeout ?? 5000

Narrow with optional chaining

1. Chain access so undefined short-circuits

opts.signal?.addEventListener("abort", onAbort)

How to prevent it

• Handle optional and indexed values with defaults or guards; noUncheckedIndexedAccess surfaces these early.

Frequently asked questions

Related guides

References

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