Avoid certain types

Docs > Code Analysis > Static Analysis Rules > Avoid certain types

Metadata

ID: typescript-best-practices/ban-types

Language: TypeScript

Severity: Notice

Category: Best Practices

Description

Some types have several ways to be defined, and some others could be dangerous. This rule suggests a consistent use of types.

Non-Compliant Code Examples

// use lower-case primitives for consistency
const str: String = 'foo';
const bool: Boolean = true;
const num: Number = 1;
const symb: Symbol = Symbol('foo');
const bigInt: BigInt = 1n;

// use a proper function type
const func: Function = () => 1;

// use safer object types
const lowerObj: Object = {};
const capitalObj: Object = { a: 'string' };

const curly1: {} = 1;
const curly2: {} = { a: 'string' };

Compliant Code Examples

// use lower-case primitives for consistency
const str: string = 'foo';
const bool: boolean = true;
const num: number = 1;
const symb: symbol = Symbol('foo');
const bigInt: bigint = 1n;

// use a proper function type
const func: () => number = () => 1;

// use safer object types
const lowerObj: object = {};
const capitalObj: { a: string } = { a: 'string' };

const curly1: number = 1;
const curly2: Record<'a', string> = { a: 'string' };