lion/packages/form-system/docs/17-validation-examples.md

Validation examples

Required Validator

The required validator can be put onto every form field element and will make sure that element is not empty. For an input that may mean that it is not an empty string, while for a checkbox group it means at least one checkbox needs to be checked.

import { html } from 'lit-html';
/* eslint-disable import/no-extraneous-dependencies */
import { LionInput } from '@lion/input';
import '@lion/input-amount/lion-input-amount.js';
import '@lion/input-date/lion-input-date.js';
import '@lion/input-email/lion-input-email.js';
import '@lion/input/lion-input.js';
import {
  DefaultSuccess,
  EqualsLength,
  IsDate,
  IsEmail,
  IsNumber,
  loadDefaultFeedbackMessages,
  MaxDate,
  MaxLength,
  MaxNumber,
  MinDate,
  MinLength,
  MinMaxDate,
  MinMaxLength,
  MinMaxNumber,
  MinNumber,
  Required,
  Validator,
} from '@lion/validate';

export default {
  title: 'Forms/Validation/Examples',
};

loadDefaultFeedbackMessages();

export const requiredValidator = () => html`
  <lion-input .validators=${[new Required()]} label="Required"></lion-input>
`;

String Validators

Useful on input elements it allows to define how many characters can be entered.

export const stringValidators = () => html`
  <lion-input
    .validators=${[new EqualsLength(7)]}
    .modelValue=${'not exactly'}
    label="EqualsLength"
  ></lion-input>
  <lion-input
    .validators=${[new MinLength(10)]}
    .modelValue=${'too short'}
    label="MinLength"
  ></lion-input>
  <lion-input
    .validators=${[new MaxLength(7)]}
    .modelValue=${'too long'}
    label="MaxLength"
  ></lion-input>
  <lion-input
    .validators=${[new MinMaxLength({ min: 10, max: 20 })]}
    .modelValue=${'that should be enough'}
    label="MinMaxLength"
  ></lion-input>
`;

Number Validators

Number validations assume that it's modelValue is actually a number. Therefore it may only be used on input that have an appropriate parser/formatter like the input-amount.

export const numberValidators = () => html`
  <lion-input-amount
    .validators="${[new IsNumber()]}"
    .modelValue="${'foo'}"
    label="IsNumber"
  ></lion-input-amount>
  <lion-input-amount
    .validators="${[new MinNumber(7)]}"
    .modelValue="${5}"
    label="MinNumber"
  ></lion-input-amount>
  <lion-input-amount
    .validators="${[new MaxNumber(7)]}"
    .modelValue="${9}"
    label="MaxNumber"
  ></lion-input-amount>
  <lion-input-amount
    .validators="${[new MinMaxNumber({ min: 10, max: 20 })]}"
    .modelValue="${5}"
    label="MinMaxNumber"
  ></lion-input-amount>
`;

Date Validators

Date validators work with real javascript dates. Use them on input-date.

export const dateValidators = () => {
  const today = new Date();
  const year = today.getFullYear();
  const month = today.getMonth();
  const day = today.getDate();
  const yesterday = new Date(year, month, day - 1);
  const tomorrow = new Date(year, month, day + 1);
  return html`
    <lion-input-date
      .validators=${[new IsDate()]}
      .modelValue=${'foo'}
      label="IsDate"
    ></lion-input-date>
    <lion-input-date
      .validators=${[new MinDate(today)]}
      .modelValue=${new Date(yesterday)}
      label="MinDate"
    ></lion-input-date>
    <lion-input-date
      .validators=${[new MaxDate(today)]}
      .modelValue=${new Date(tomorrow)}
      label="MaxDate"
    ></lion-input-date>
    <lion-input-date
      .validators=${[new MinMaxDate({ min: new Date(yesterday), max: new Date(tomorrow) })]}
      .modelValue=${new Date(today)}
      label="MinMaxDate"
    ></lion-input-date>
  `;
};

Email Validator

export const emailValidator = () => html`
  <lion-input-email
    .validators="${[new IsEmail()]}"
    .modelValue="${'foo'}"
    label="IsEmail"
  ></lion-input-email>
`;

Validation Types

When defining your own component you can decide to allow for multiple types of validation. By default only error is used, however there are certainly use cases where warning or success messages make sense.

export const validationTypes = () => {
  try {
    class MyTypesInput extends LionInput {
      static get validationTypes() {
        return ['error', 'warning', 'info', 'success'];
      }
    }
    customElements.define('my-types-input', MyTypesInput);
  } catch (err) {
    // expected as it is a demo
  }
  return html`
    <style>
      .demo-types-input {
        padding: 0.5rem;
      }
      .demo-types-input[shows-feedback-for~='success'] {
        background-color: #e4ffe4;
        border: 1px solid green;
      }
      .demo-types-input[shows-feedback-for~='error'] {
        background-color: #ffd4d4;
        border: 1px solid red;
      }
      .demo-types-input[shows-feedback-for~='warning'] {
        background-color: #ffe4d4;
        border: 1px solid orange;
      }
      .demo-types-input[shows-feedback-for~='info'] {
        background-color: #d4e4ff;
        border: 1px solid blue;
      }
    </style>
    <my-types-input
      .validators="${[
        new Required(),
        new MinLength(7, { type: 'warning' }),
        new MaxLength(10, {
          type: 'info',
          getMessage: () => `Please, keep the length below the 10 characters.`,
        }),
        new DefaultSuccess(),
      ]}"
      .modelValue="${'exactly'}"
      label="Validation Types"
      class="demo-types-input"
    ></my-types-input>
  `;
};

Custom Validators

Here is an example how you can make your own validator and providing the error messages directly within. You can even hard code localization in there if needed or you can use a localization system.

export const customValidators = () => {
  class MyValidator extends Validator {
    static get validatorName() {
      return 'myValidator';
    }
    execute(modelValue, param) {
      return modelValue !== param;
    }
    static getMessage({ fieldName, modelValue, params: param }) {
      if (modelValue.length >= param.length - 1 && param.startsWith(modelValue)) {
        return 'Almost there...';
      }
      return `No "${param}" found in ${fieldName}`;
    }
  }
  return html`
    <lion-input
      label="Custom validator"
      help-text="Type 'mine' please"
      .validators="${[new MyValidator('mine')]}"
      .modelValue="${'mi'}"
    ></lion-input>
  `;
};

Default messages

To get default validation messages you need to import and call the loadDefaultFeedbackMessages function once in your application.

Sometimes the default messages don't make sense for your input field. In that case you want to override it by adding a getMessage function to your validator.

export const defaultMessages = () => html`
  <lion-input
    .validators="${[new EqualsLength(4, { getMessage: () => '4 chars please...' })]}"
    .modelValue="${'123'}"
    label="Custom message for validator instance"
  ></lion-input>
  <lion-input
    .validators="${[
      new EqualsLength(4, {
        getMessage: ({ modelValue, params: param }) => {
          const diff = modelValue.length - param;
          return `${Math.abs(diff)} too ${diff > 0 ? 'much' : 'few'}...`;
        },
      }),
    ]}"
    .modelValue="${'way too much'}"
    label="Dynamic message for validator instance"
  ></lion-input>
`;

Override fieldName

In the scenario that the default messages are correct, but you only want to change the fieldName, this can both be done for a single specific validator or for all at once.

export const overrideFieldName = () => html`
  <lion-input
    .validators="${[new EqualsLength(4, { fieldName: 'custom fieldName' })]}"
    .modelValue="${'123'}"
    label="Custom fieldName for 1 validator"
  ></lion-input>
  <lion-input
    .validators="${[new Required(), new EqualsLength(4)]}"
    .fieldName="${'custom fieldName'}"
    .modelValue="${'123'}"
    label="Custom fieldName for all validators"
  ></lion-input>
`;

Asynchronous validation

export const asynchronousValidation = () => {
  function pause(ms = 0) {
    return new Promise(resolve => {
      setTimeout(() => {
        resolve();
      }, ms);
    });
  }
  class AsyncValidator extends Validator {
    constructor(...args) {
      super(...args);
    }
    static get validatorName() {
      return 'asyncValidator';
    }
    static get async() {
      return true;
    }
    async execute() {
      console.log('async pending...');
      await pause(2000);
      console.log('async done...');
      return true;
    }
    static getMessage({ modelValue }) {
      return `validated for modelValue: ${modelValue}...`;
    }
  }
  return html`
    <style>
      lion-input[is-pending] {
        opacity: 0.5;
      }
    </style>
    <lion-input
      label="Async validation"
      .validators="${[new AsyncValidator()]}"
      .modelValue="${'123'}"
    ></lion-input>
  `;
};

Dynamic parameter change

export const dynamicParameterChange = () => {
  const beginDate = new Date('09/09/1990');
  const minDateValidatorRef = new MinDate(beginDate, {
    message: 'Fill in a date after your birth date',
  });
  return html`
    <lion-input-date
      label="Birth date"
      help-text="Adjust this date to retrigger validation of the input below..."
      .modelValue="${beginDate}"
      @model-value-changed="${({ target: { modelValue, errorState } }) => {
        if (!errorState) {
          // Since graduation date is usually not before birth date
          minDateValidatorRef.param = modelValue;
        }
      }}"
    ></lion-input-date>
    <lion-input-date
      label="Graduation date"
      .modelValue="${new Date('09/09/1989')}"
      .validators="${[minDateValidatorRef]}"
    ></lion-input-date>
  `;
};

Disabled inputs validation

According to the W3C specs, Disabled fields should not be validated. Therefor if the attribute disabled is present on a lion-input it will not be validated.

export const disabledInputsValidation = () => html`
  <lion-input
    disabled
    .validators=${[new EqualsLength(7)]}
    .modelValue=${'not exactly'}
    label="EqualsLength"
  ></lion-input>
  <lion-input
    disabled
    .validators=${[new MinLength(10)]}
    .modelValue=${'too short'}
    label="MinLength"
  ></lion-input>
  <lion-input
    disabled
    .validators=${[new MaxLength(7)]}
    .modelValue=${'too long'}
    label="MaxLength"
  ></lion-input>
  <lion-input
    disabled
    .validators=${[new MinMaxLength({ min: 10, max: 20 })]}
    .modelValue=${'that should be enough'}
    label="MinMaxLength"
  ></lion-input>
`;