Type for non-null and non-undefined in TypeScript


TypeScript’s type computation does support complement of type, so we cannot simply define a type for not-null.

This is a workaround to create a type for non-null and non-undefined:

(in short, we compute the wanted complement set by hand)

  • Use TypeScript 2.2 which introduced object type.
  • Set "strictNullChecks": true in tsconfig.json to separate null / undefined and other types.

The complement set of type null | undefined can then be expressed as number | string | boolean | symbol | object.