Skip to main content

hoyams

the validation tool nobody asked for | hoyams = hold on you are missing something

Concept

Rules are defined via a callback which retuns true or an error String. This is so that you can define rules by using an or operator like this:

new Rule((v) => typeof v === "string" || "is not a string");

or this:

new Rule((v) =>
  typeof v === "string" && !!v.match(/^\w+@\w+\.\w+$/) ||
  "no valid email"
);

  • If a executing a validation completes without an error an object with the same structure as the object given is returned.

  • For creating powerful nested object rules there are some primites given: How to use

ValidationError

If a validation failes an custom Error (instance of ValidationError) will be thrown. ValidationError has a custom proprty map which retunr the error message(s) in the same structure as the rule object.

How to use

Rule

simple single rule definition

const rule = new Rule(
  (v) => typeof v === "string" || "is not a string",
);
rule.validate(obj);

ValidationError.map: "is not a string"

Ruleset

define multiple rules for a single property

const rule = new Ruleset([
  (v) => typeof v === "string" || "is not a string",
  (v) => v.length > 5 || "too short",
]);
rule.validate(obj);

ValidationError.map: ["is not a string", "too short"]

ArrayRule

define a rule which applies to all elements in an array

const rule = new ArrayRule(
  new Rule((v) => typeof v === "string" || "is not a string"),
);
rule.validate(arr);

ValidationError.map: "is not an array" or [null, "is not a string", ...]

ObjectRule

define different rules to specific proprties in an object

const rule = new ObjectRule({
  name: new Rule((v) => typeof v === "string" || "is not a string"),
});
rule.validate(arr);

ValidationError.map: "is not an object" or { name: "is not a string" }

More complex example

example to define more complex rules

const rule = new ObjectRule({
  id: new Rule((v) => typeof v === "number" || "not a number"),
  user: {
    name: new Rule((v) => typeof v === "string" || "no string"),
    tags: new ArrayRule(
      new Ruleset([
        (v) => typeof v === "string" || "no string",
        (v) => typeof v === "string" && v.length > 2 || "too short",
      ]),
    ),
    email: new Rule((v) =>
      typeof v === "string" && !!v.match(/^\w+@\w+\.\w+$/) || "no valid email"
    ),
  },
});

try {
  const validated = rule.validate(obj);
} catch (e) {
  if (e instanceof ValidationError) {
    const errorMap = e.map;
  } else {
    throw e;
  }
}

You can also use the validate helper function directly. f/e/ if you need a rule only time:

try {
  const validated = validate(
    {
      id: "hey",
    },
    {
      id: new Rule((v) => typeof v === "number" || "not a number"),
    },
  );
} catch (e) {
  if (e instanceof ValidationError) {
    const errorMap = e.map;
  } else {
    throw e;
  }
}