validateFields

We saw that the form validator supports the ability to perform field-level validation in addition to form-level validation. To validate one or some fields, an array of field names can be supplied in the validation context. While straightforward, this code is verbose. For that reason, Strickland's form validator provides a validateFields helper function.

Here is some application code that performs field-level validation without the validateFields helper.

import validate, {
    form, required, length, range
} from 'strickland';

const personValidator = form({
    firstName: [
        required(),
        length({minLength: 2, maxLength: 20})
    ],
    lastName: [
        required(),
        length({minLength: 2, maxLength: 20})
    ],
    birthYear: range({min: 1900, max: 2018})
});

// Initialize the person with only a firstName
let person = {
    firstName: 'Stanford'
};

// Validate the firstName field
let result = validate(personValidator, person, {
    form: {
        fields: ['firstName']
    }
});

The validateFields helper is available from the validator created using the form validator factory.

import validate, {
    form, required, length, range
} from 'strickland';

const personValidator = form({
    firstName: [
        required(),
        length({minLength: 2, maxLength: 20})
    ],
    lastName: [
        required(),
        length({minLength: 2, maxLength: 20})
    ],
    birthYear: range({min: 1900, max: 2018})
});

// Initialize the person with only a firstName
let person = {
    firstName: 'Stanford'
};

// Validate the firstName field
let validationResult = personValidator.validateFields(person, ['firstName']);

Once initial validation has occurred, validateFields can accept existing validation results to be updated during field-level validation.

// The firstName field has already been validated
// Validate the lastName field

validationResult = personValidator.validateFields(
    person,
    ['lastName'],
    validationResult
);