Utilize utility types rather than create a new interface

Medium

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Clean codeTypescriptAdd example

What to do

• Use utility types (Omit, Union, Pick ...)

Prevent problems

• Copy-Paste
• Duplication
• Readability

Explanation

Using spectific interface to avoid useless data and permit interface segregation. When we need some properties from one or several interfaces, we should use utility types.

Violations should be raised when, within the same file, there exists 'type' or 'interface' that have properties which are defined in another type or variable.

For instance:

interface User {
    firstName: string;
    lastName: string;
}

interface FullUser {
    firstName: string;
    lastName: string;  
    address: string;
}

is an issue since FullUser contains all properties defined in the interface User.

Examples

Example 1:

Negative

Incorrect implementation that violates the practice.

interface User {
    id: string;
    firstName: string;
    lastName:string;
    email: string;
}

interface UserWithoutId  {
    firstName: string;
    lastName:string;
    email: string;
}

const user: UserWithoutId = {
    firstName: 'John',
    lastName: 'Test',
    email: 'john.test@test.com'
}