callback validator

Check if the input value passes a callback method

Options

Using with form field

The HTML attributes are used to set the validator options via the Declarative plugin

(* denotes a required option)

Name	HTML attribute	Type	Description
`callback`*	`data-fv-callback___callback`	`Function`	The callback method
`message`	`data-fv-callback___message`	`String`	The error message

The callback method must follow the format below:

function(input) {
    // input is an object of
    // {
    //      value: The field value,
    //      options: The callback validator options
    // }

    // Check the field validity
    return true;    // or false
}

If you want to return a dynamic message, the callback function must return an object containing the valid and message members:

function(input) {
    // input is an object of
    // {
    //      value: The field value,
    //      options: The callback validator options
    // }

    // ... Do your logic checking
    if (...) {
        return {
            valid: true,    // or false
            message: 'The error message'
        };
    }

    return {
        valid: false,       // or true
        message: 'Other error message'
    };
}

Look at the Alias plugin if you want to have multiple callbacks on the same field

Using with ES6 module

// You might need to change the importing path
import callback from 'formvalidation/dist/es6/validators/callback';

const result = callback().validate({
    value: ...,
    options: {
        callback: ...,
    },
},
});
/*
result is an object of
{
    valid: true or false,
    message: The error message
}
*/

Basic example

In the following form, user is asked to enter a correct answer of simple operation which is generated randomly.

callback validator

ES6 Module Example

The following snippet shows how to use the callback validator with ES6 module to check if a password is strong or weak:

// You might need to change the importing path
import callback from 'formvalidation/dist/es6/validators/callback';

// A very simple method to check the strength of a password
const validatePassword = function (input) {
    const value = input.value;
    if (value === '') {
        return { valid: true };
    }

    if (value.length < 8) {
        return {
            valid: false,
            message: 'Password must have at least 8 characters',
        };
    }

    if (value === value.toLowerCase()) {
        return {
            valid: false,
            message: 'Password must have at least one uppercase character',
        };
    }

    if (value === value.toUpperCase()) {
        return {
            valid: false,
            message: 'Password must have at least one lowercase character',
        };
    }

    if (value.search(/[0-9]/) < 0) {
        return {
            valid: false,
            message: 'Password must have at least one digit',
        };
    }

    return { valid: true };
};

const res1 = callback().validate({
    value: '123456',
    options: {
        callback: validatePassword,
    },
});
// res1.valid === false

const res2 = callback().validate({
    value: 'not.contains.upper',
    options: {
        callback: validatePassword,
    },
});
// res2.valid === false

const res3 = callback().validate({
    value: 'not@CONTAIN@digit',
    options: {
        callback: validatePassword,
    },
});
// res3.valid === false

const res4 = callback().validate({
    value: 'v@l1dP@@',
    options: {
        callback: validatePassword,
    },
});
// res4.valid === true

callback validator

Options

Basic example

ES6 Module Example

See also