1. atLeastOne, at least one of the controls should satisfy the provided validator.

atLeastOne = (validator, controls: string[] | null) => ...

2. atLeastOneConditionally, at least one of the controls should satisfy the provided validator if the dependedControl has the dependedValue.

atLeastOneConditionally = (
    validator: ValidatorFn,
    dependedControl: string,
    dependedValue: any,
    controls: string[] | null = null
  ) => ...

3. requiredConditionally, make controls required, if the dependedControl has the dependedValue.

requiredConditionally = (
    dependedControl: string,
    dependedValue: any,
    controls: string[] | null = null
  ) => ...

4. requiredConditionally2, make controls required, if the dependedControl has the dependedValue and the dependedControl2 has the dependedValue2.

requiredConditionally2 = (
  dependedControl: string, dependedValue: any) =>
  (
    dependedControl2: string,
    dependedValue2: any,
    controls: string[] | null = null
  ) => ...

5. conditionalValidator, apply validator if predicate return true.

conditionalValidator =
  (predicate: () => boolean, validator: ValidatorFn) => ...