Use of the any type disables the type check system around that variable, defeating the purpose of Typescript which is to provide type safe code. Additionally, the use of any hinders code readability, since it is not immediately clear what type of value is being referenced. It is better to be explicit about all types. For a more type-safe alternative to any, use unknown if you are unable to choose a more specific type.

Invalid:

const someNumber: any = "two";
function foo(): any {
  return undefined;
}

Valid:

const someNumber: string = "two";
function foo(): undefined {
  return undefined;
}