isType typeguard

isType.ts

/**
 * 
 * @param {any} item item you want to typecheck
 * @param {(keyof T)[]} keys keys that should be present in the type and not be undefined
 * @returns {boolean} Later in code item is of T type on success
 */

export const isType = <T extends unknown> (item: unknown, keys: (keyof T)[]):item is T  => {
  return item !== null && keys.every(key => (item as T)[key as keyof T] !== undefined)
}