When applications consume validation results, they often need to augment or transform the validation results from the validators. Not all of those scenarios can be accomplished through Validator Result Props, and a different mechanism is needed. Strickland's formatResult function can help. formatResult wraps a supplied validator and uses a specified result formatter function to augment or transform the result from the validator.


The formatResult function accepts two parameters:

  1. The result formatter function

  2. The validator to wrap

The parameters are specified in this order to make it easy to use formatResult.bind() with a result formatter function.

The result formatter function will be called with 2 parameters.

  1. The result object from the validator, already normalized through Strickland's validate function.

  2. An object containing {value, context} where value is the value that was validated and context is the validation context provided.


The following example shows how formatResult can be used to augment the result of a very basic validator. The formatter uses the validated value to generate a message validation result prop.

import validate, {formatResult} from 'strickland';

function letterA(value) {
    return (value === 'A');

function withMessage(result, {value}) {
    return {
        message: `The letter "A" was expected, but "${value}" was supplied`

const validator = formatResult(withMessage, letterA);

const result = validate(validator, 'B');

    result = {
        isValid: false,
        value: 'B',
        message: 'The letter "A" was expected, but the value "B" was supplied'

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