Terminology

In this section, we are going to explain the basic terminology.

Rule

A rule is a function that takes at least one argument (value) and validates the data. It should return a true or false value as a return.

The following type definition is the definition of a rule function.

type RuleFunction = (...args: any[]) => Promise<boolean> | boolean;

The first parameter of a rule function should be the value that will be validated always.

export default (value: any): boolean => {
  // Return `true` if the `value` is valid.
  return true;
};

A rule function always might have more parameters if it needs them. For example, if you want to check the minimum string size, the rule function should have to parameter like the following example.

export default (value: any, size: any): boolean => {
  // Return `true` if the `value` is valid.
  return true;
};

A rule should be able to execute directly.

import { isRequired } from "robust-validator";

const result = isRequired("data");

WARNING

Each rule function should validate only one thing. For example, the email validation should NOT check if the data is provided. Otherwise, a rule function can not check the optional data.

That's why null and undefined values are acceptable for all rules except the required.

If you want to check if the data is provided and is a valid email, you should use two rules (required, email) at the same time.

Definition

The definition means which rule sets will be executed for data.

It should be an object like the following example:

const definition = {
  email: "required|email",
  name: "required|min:1|max:50",
  surname: "required|min:1|max:50",
};

For each data property, the rule names should be defined.

The | should be used to be able to use multiple rule names at the same time:

required|email|alpha

All possible rule parameters should be defined after the : operator. If there is more than one parameter, they must be separated using commas.

required|min:1|max:50|between:1,50