7 Patterns That Separate Senior Code from Junior Code (With TypeScript Examples)

The Real Difference Between Junior and Senior Code It's not the algorithms. It's not the frameworks. It's the implicit knowledge about what goes wrong in production. Here are the patterns senior developers apply without thinking -- and junior developers learn the hard way. 1. Defensive Data Access // Junior: assumes data exists const userName = user.profile.name.first // Senior: handles the whole chain const userName = user?.profile?.name?.first ?? 'Anonymous' // Or for API responses: const items = response?.data?.items ?? [] const total = response?.data?.pagination?.total ?? 0 2. Explicit Error States in UI // Junior: handles loading and success if (loading) return <Spinner /> return <DataTable data={data} /> // Senior: handles all states if (loading) return <Spinner /> if (error) return <ErrorMessage error={error} retry={refetch} /> if (!data || data.length === 0) return <EmptyState /> return <DataTable data={data} /> // Empty state is the one ever