The non-null assertion operator (!) tells TypeScript to trust you when you say a value isn't null or undefined. But this trust comes at a cost: runtime crashes that TypeScript could have prevented. Learn why this operator undermines type safety and what to use instead.

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The non-null assertion operator (!) in TypeScript bypasses type safety by forcing the compiler to treat potentially nullable values as non-null, leading to runtime crashes. Instead of using this operator, developers should employ safer alternatives: optional chaining for nested property access, nullish coalescing for default values, conditional operators for explicit branching, type guards for reusable validation, and assertion functions for enforcing invariants. These approaches maintain type safety while handling null and undefined values appropriately, following fail-fast principles and preventing silent failures.

Stop Using TypeScript's Exclamation Mark

I don’t agree, there are occasions I want to say that “I know” this is not null, for example process.env.* , it is defined as a string | undefined… but I know it has a value and I don’t want needlessly to check for null.

Every tool has its use case and purpose, never say never.

never say never, I believe in TS supremacy

Same with Kotlin. It’s an anti-pattern, only to be used for quick &amp; dirty prototyping. Not something I would even run in a development environment outside of my computer.