What is Type-safe?

TL;DR:

Type-safe ensures data types are correct and consistent in programs, especially in modern languages like TypeScript. Key characteristics include using generic and template literal types, the builder pattern, automatic type inference, and reducing type duplication. Examples of TypeScript projects utilizing type-safe design include Zod, tRPC, Hono, and Elysia.

Many in the programming community frequently mention "type-safe," yet few attempt to define it clearly. For more clarity, let's break down what type-safe means in the context of modern programming languages like TypeScript in my understanding.

Type-safe is a design pattern that ensures data types are correct and consistent within a program. This pattern is particularly valuable in modern programming languages like TypeScript, which boasts a powerful type system to enhance program correctness and reliability.

The Traditional Type

When I've mentioned the traditional type, I mean the type that is defined in the program. Not only TypeScript type, but also the type in other programming language like Java, C#, etc.

The traditional type is a way to define the data type in the program. It can be a primitive type like number, string, boolean, etc. or a complex type like interface, class, etc.

For example, in TypeScript, we can define a type like this:

interface Person {
  name: string;
  age: number;
}

Characteristics of Type-safe

Many libraries and frameworks provide type-safe support, here is some characteristics of type-safe when the they claim that they are type-safe:

• Generic: They use generic types
• Template Literal Types: They use template literal types
• Builder Pattern: They use builder pattern
• Automatic Type Inference: They use automatic type inference passing through the function and generic types
• Reduce Type Duplicate Definition: They reduce the duplicate definition of types