This content originally appeared on DEV Community and was authored by Manoj Gohel
In TypeScript, both Types and Interfaces are used to define the types of objects. However, they have different uses and features. Both can help developers constrain the types of variables and objects when writing code, thereby reducing errors and improving code readability.
- type:
typeis a type alias used to define an alias for any type. This is not limited to object types; it can also define primitive types, union types, intersection types, etc. For example:
// Define an alias for a primitive type
type Name = string;
// Define an alias for an object type
type User = {
id: number;
name: string;
};
// Define a union type
type Status = 'active' | 'inactive' | 'suspended';
// Define an intersection type
type Person = {
name: string;
} & {
age: number;
};
- interface:
interfaceis used to define the structure of an object and can be extended by inheriting other interfaces.interfaceis mainly used to define the structure and implementation constraints of classes. For example:
// Define an object interface
interface User {
id: number;
name: string;
}
// Interface inheritance
interface Admin extends User {
role: string;
}
// Interface implementation in a class
class Person implements User {
id: number;
name: string;
constructor(id: number, name: string) {
this.id = id;
this.name = name;
}
}
Why prioritize using Types?
In TypeScript, there has been an ongoing debate about whether to use Types or Interfaces for type definitions. Although both can be used to create reusable structures for variables, function parameters, and return values, in most cases, we should prioritize using Types. Here are four main reasons:
1. Support for Union Types
type can define union types, which is something interface cannot do.
type StringOrNumber = string | number;
2. Support for String Literal Types
`type` can define string literal types, which can be very useful in certain scenarios.
type Status = 'success' | 'error' | 'pending';
## **3\.** Immutability
`type` is immutable, meaning once defined, it cannot be changed through extension or merging. This ensures the stability and consistency of the type. In contrast, `interface` can be declared multiple times and merged, which might lead to unexpected behaviors.
type User = {
email: string;
}
// Will cause an error because it cannot be declared multiple times
type User = {
password: string;
}
interface User {
email: string;
}
// The two declarations will be merged, and the final User interface will contain both email and password properties.
interface User {
password: string;
}
4. Support for Conditional Types
type supports conditional types, which can be used for more complex type definitions.
type IsString<T> = T extends string ? 'yes' : 'no';
In summary, prioritizing type provides greater flexibility and powerful type expression capabilities, especially when dealing with complex types and logic. type can better meet your needs. Therefore, I always choose to use type first, as it enhances code type safety and maintainability.
This content originally appeared on DEV Community and was authored by Manoj Gohel
Manoj Gohel | Sciencx (2024-06-24T05:12:09+00:00) Why I Always Choose to Use Types Instead of Interfaces？. Retrieved from https://www.scien.cx/2024/06/24/why-i-always-choose-to-use-types-instead-of-interfaces%ef%bc%9f/
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