@module {function} can-validate-validatejs
@parent can-data-validation
@collection can-ecosystem
@group can-validate-validatejs.methods 1 Methods
@package ../package.json

@description Create [can-validate.validator] functions using [validate.js](https://validatejs.org/).

@signature `makeValidator(constraints)`

Returns a validator function that can be used to validate a single value.

  ```js
const validateAge = makeValidator( {
	numericality: true
} );
```


  @param {Object} constraints An object of definitions used by the Validate.js library to run validations on a value.

  @return {Validator} A validator type function that takes a value and validates it against the provided constraints.

@body

## Usage

A validator can be created either for a single value or for many values.  More information on how to configure Validate.JS constraints can be found [here](https://validatejs.org/#validators).

### Single value validation

Using the [Validate.js](https://validatejs.org/) library validators and configuration, call `makeValidator` and pass the desired constraints. The resulting function can then be used to validate specific values.

```js
import makeValidator from "can-validate-validatejs";
const validateAge = makeValidator( {
	numericality: true
} );

const age = "hello";
validateAge( age ); //> ['is not a number']

const anotherAge = 35;
validateAge( anotherAge ); //> undefined
```

### Multiple value validation

Using the [can-validate-validatejs.many] works similar to `makeValidator`, except that `makeValidator.many` produces a validator that expects an object of values. The validator will run constraints on respective values based on the keys provided.

```js
import makeValidator from "can-validate-validatejs";
const validatePerson = makeValidator.many( {
	age: {
		numericality: true
	},
	name: {
		presence: true
	}
} );

const invalidPerson = {
	name: "",
	age: "hello"
};
validatePerson( invalidPerson ); //> {name: ['is required'], age: ['is not a number']}

const validPerson = {
	name: "Juan",
	age: 35
};
validatePerson( validPerson ); //> undefined
```