Always use appropriate guards or type checks before accessing potentially null or undefined values. Prefer type-safe guard methods that provide both runtime protection and TypeScript type narrowing over manual null checks. For Angular resource APIs, use `hasValue()` before accessing `value()` since it acts as both an error guard and type guard that narrows the type to remove `undefined`: ```ts const firstName = computed(() => { if (userResource.hasValue()) { // hasValue() guards against errors and narrows type return userResource.value().firstName; } return undefined; // fallback for error/loading states }); ``` For optional component inputs or router data, prefer making inputs required when possible rather than handling undefined throughout your component: ```ts // Prefer this - required input settings = input.required(); // Over this - optional input requiring null checks settings = input(); // Would need settings()?.theme ``` This pattern prevents runtime errors while leveraging TypeScript's type system to catch potential null reference issues at compile time.