Type assertion is explicitly telling the compiler that we want to treat the entity as a different type. However, if we add a type assertion for a variable which is automatically inferred with the same type already then it is unnecessary to define the type explicitly.

Using a type assertion that does not change the type of an expression is unnecessary and should be avoided for a cleaner code.

Bad Practice

// Types of 'foo' and 'bar' are already inferred as 'number', explicit type assertion in unnecessary
let foo = 3 as number;
let bar = <number>3;

function foobar(x: number): number {
  return x!; // Type of 'x' is 'number' and is not 'null' or 'undefined'. Non-null assertion is unnecessary
}

type NewType = number;
let baz = 3 as NewType
let qux = <NewType>3

Recommended

const foo = [1, 2] as const; // Using 'as const' enforces the array to be readonly

function foobar(x: number | undefined): number {
  return x!;
}

DevClad-Inc / devclad

No ignore rules found