input-validation-util

A library to validate and transform input value using declarative rules

Installation

npm i input-validation-util

Usage

Import,

import {createInputValidator} from 'input-validation-util';

Example 1: using correct input

Define rules,

const validate = createInputValidator([
    {
        ruleName: 'is / can be number',
        test: value => !isNaN(value),
        transformValue: value => Number(value)
    },
    {
        ruleName: 'round number',
        transformValue: (value, transformedValue) =>
            Math.round(transformedValue)
    },
    {
        ruleName: 'meet minimum value',
        test: (value, transformedValue) => transformedValue >= 10,
        resetInvalidInput: (value, transformedValue) => `Reset to 10`,
        errorMessage: '5 is less than 10'
    }
]);

• ruleName is arbitrary and is the only compulsory option
• test callback
  • returns a boolean based on your custom validation logic
  • returns true for valid input
  • first failed rule will be available in the validation result as firstFailedRule
  • all failed rules will be available in the validation result as allFailedRules
• transformValue callback
  • returns a value using your custom transformation logic
  • the transformed value will be available as the second parameter in test, transformValue and resetInvalidInput callbacks of subsequent rules
  • it is run in all conditions when
    • test callback returns true
    • test callback is not provided
    • except: test callback returns false
  • transformed value returned from the last rule will be available in the validation result as transformedValue
• resetInvalidInput callback
  • returns a custom value
  • it is run only when test callback returns false
  • value returned from the first failed rule will be available in the validation result as resetInputValue
  • it is named as such because it is intended to provide a value to reset invalid input
• errorMessage
  • custom error message string

Validate input,

const result = validate('20.5');

Use the validation result,

if (result.valid) {
    // result.inputValue === '20.5'
    // result.transformedValue === 21
    // result.firstFailedRule === null
    // result.allFailedRules.length === 0
    // result.resetInputValue === null
}

Example 2: using incorrect input

Validate input,

const result = validate(5);

Use the validation result,

if (!result.valid) {
    // result.inputValue === 5
    // result.transformedValue === 5
    // result.firstFailedRule.ruleName === 'meet minimum value'
    // result.allFailedRules.length === 1
    // result.resetInputValue === 'Reset to 10'
	// result.firstFailedRule.errorMessage === '5 is less than 10'
}

API Reference

• createInputValidator(rules: Rule | Rule[]): (value: any) => Result

• Rule

interface Rule {
    test?: (value: any, transformedValue: any) => boolean;
    resetInvalidInput?: (value: any, transformedValue: any) => any;
    transformValue?: (value: any, transformedValue: any) => any;
    ruleName: string;
    errorMessage?: string;
}

• Result

interface Result {
    firstFailedRule: Rule | null;
    allFailedRules: Rule[];
    valid: boolean;
    inputValue: any;
    transformedValue: any;
    resetInputValue: any;
}