Svelte Form

Simple Svelte Form model handler and form fields validation library. It is designed to give maximum freedom in the actual input component construction, i.e. there are not actual build-in input components, rather examples how to build one.

To see the details code documentation, please read the Code Documentation.

Quick Links

Webpack Setup
Rollup Setup

Table of Content

Svelte Form

Installation via NPM or Yarn

npm install -D @spaceavocado/svelte-form

yarn add @spaceavocado/svelte-form -D

Webpack Setup

Please see the Svelte Webpack Template. Important setup in the webpack.config.js:

resolve: {
  // This alias is important to prevent svelte mismatch
  // between your code, and the 3rd party components.
  alias: {
    svelte: path.resolve('node_modules', 'svelte')
  },
  extensions: ['.mjs', '.js', '.svelte'],
  mainFields: ['svelte', 'browser', 'module', 'main']
},

module: {
  rules: [
    {
      test: /\.svelte$/,
      // Do not exclude: /(node_modules)/ since the router 
      // components are located in the node_modules
      use: {
        loader: 'svelte-loader',
        options: {
          emitCss: true,
          hotReload: true
        }
      }
    }
  ]
}

Rollup Setup

rollup.config.js:

import babel from 'rollup-plugin-babel';
import resolve from 'rollup-plugin-node-resolve';
import commonjs from 'rollup-plugin-commonjs';
import svelte from 'rollup-plugin-svelte';

export default {
  input: './src/index.js',
  output: {
    file: './dist/bundle.js',
    format: 'iife'
  },
  plugins: [
    resolve(),
    commonjs({
      include: 'node_modules/**',
    }),
    svelte(),
    babel({
      exclude: 'node_modules/**',
    }),
  ]
}

Essentials

Note: All code below uses ES2015+.

Create the Form

form.svelte:

import createForm from '@spaceavocado/svelte-form';

// An example of a form without validation
const form = createForm({
  username: '',
  password: '',
});

To get more details about the createForm method, please see Create Form.

Input Binding

form.svelte:

<script>
import createForm from '@spaceavocado/svelte-form';
import TextInput from './input/text.svelte';

// An example of a form without validation
const form = createForm({
  username: '',
  password: '',
});
</script>

<TextInput form={form} name='username' />

text.svelte:

<script>
  // Props
  export let form;
  export let name;

  // Get the form field
  $: field = form.field(name);
  // Value svelte store
  $: value = field.value;
  // State svelte store, {valid: boolean, error: string}
  $: state = field.state;
</script>

<div class="input" class:error="{$state.valid === false}">
  <input type="text" bind:value="{$value}" />
  <p class="validation">{$state.error}</p>
</div>

<style lang="scss">
.input {
  .validation {
    display: none;
  }
  &.error {
    .validation {
      display: block;
    }
  }
}
</style>

The state store is a derived store based on the value store, performing the input validation each time the value changes.
The form.field(name) method gets the field stores, for more details see Form Field Object.

Form State

The form state is a svelte store holding the form validation state.

form.svelte:

import createForm from '@spaceavocado/svelte-form';

// An example of a form without validation
const form = createForm({
  username: '',
  password: '',
});

// You can directly subscribe to form state change
form.subscribe((f) => console.log(f.valid));
// or shorthand access.
console.log($form.valid)

To get more details about the form, please see Form Object.

Form Data

You can get the current form date anytime by calling:

import createForm from '@spaceavocado/svelte-form';

// An example of a form without validation
const form = createForm({
  username: '',
  password: '',
});

// Get the form current data
const data = form.data();

Form Field Validation

Validation functions could be passed for individual form fields:

import createForm from '@spaceavocado/svelte-form';
import {required, email} from '@spaceavocado/svelte-form';

// An example of a form without validation
const form = createForm(
  // Form fields
  {
    username: '',
    password: '',
  },
  // Form validation - optional
  // Collection of validation rules or single rule.
  {
    username: [
      required('This field is required'),
      email('Invalid email format')
    ],
    password: required('This field is required'),
  }
);

More information:

Builtin Validation Rules.
Custom Validation Rule.

Builtin Validation Rules

Required

import {required} from '@spaceavocado/svelte-form';

// Create new rule
const rule = required('Error message');

Equal

import {equal} from '@spaceavocado/svelte-form';

// The value must be equal to 5
const rule = equal('Error message', 5);

// Equal can accept fn(val)->boolean as an argument for a custom
// equality matching.
const customMatcherRule = equal('Error message', (val) => {
  return val === 5;
});

Email

import {email} from '@spaceavocado/svelte-form';

// Create new rule
const rule = email('Error message');

URL

import {url} from '@spaceavocado/svelte-form';

// Create new rule
const rule = url('Error message');

Min

import {min} from '@spaceavocado/svelte-form';

// The value must be 5 and more.
const rule = min('Error message', 5);

Max

import {max} from '@spaceavocado/svelte-form';

// The value must be 5 and less.
const rule = max('Error message', 5);

Between

import {between} from '@spaceavocado/svelte-form';

// The value must be between 5 and 10 inclusively.
const rule = between('Error message', 5, 10);

Regular Expression

import {rx} from '@spaceavocado/svelte-form';

// The value must match custom regular expression.
const rule = rx('Error message', /\d+\.\d+/);

Ignore Empty

This is a special rule which might be used to the ignore empty fields, i.e. any other validation rules will be tested only if the value in not empty.

import {ignoreEmpty, url} from '@spaceavocado/svelte-form';

// An example usage
const form = createForm(
  // Form fields
  {
    website: '',
  },
  // URL validation will be tested only if the website in not empty.
  {
    website: [
      ignoreEmpty(),
      url('Invalid URL'),
    ],
  }
);

Custom Validation Rule

Custom validation rule must be a function accepting a tested value, and expected to return true when valid, or error message string in not valid, e.g.:

const invoice = (msg) => (value) => {
  if (value.match(/inv-\d+/) === null) {
    return msg;
  }
  return true;
}

// The actual rule expected by the form field, e.g. fn(val)->true|string
const rule = invoice('Invalid invoice number');

Trigger Form Validation

Validation could be trigger all fields in this manner:

import createForm from '@spaceavocado/svelte-form';
import {required, email} from '@spaceavocado/svelte-form';

// An example of a form without validation
const form = createForm(
  // Form fields
  {
    username: '',
    password: '',
  },
  // Form validation - optional
  // Collection of validation rules or single rule.
  {
    username: [
      required('This field is required'),
      email('Invalid email format')
    ],
    password: required('This field is required'),
  }
);

// Trigger validation of all fields
form.validate();

API

To see the details code documentation, please read the Code Documentation

Create Form

import createForm from '@spaceavocado/svelte-form';

// Please see the opts below.
const formOpts = {};

// Please see the Form object for details on returned object
const form = createForm(
  // Form fields
  {
    username: '',
    password: '',
  },
  // Form validation - optional
  // Collection of validation rules or single rule.
  {
    username: [
      required('This field is required'),
      email('Invalid email format')
    ],
    password: required('This field is required'),
  },
  // Form options - optional
  formOpts,
);

Form Options

Property	Description	Type
onCreateValidation	Validate form fields when the form is created. Defaults to false.	boolean

Form Object

Property	Description	Type
subscribe	Svelte store, context {valid: boolean}.	function
field	Get form field observable value and state. Signature fn(key), returns Form Field Object.	function
data	Get all form fields data. Signature fn().	function

Form Field Object

Property	Description	Type
value	Svelte store, context: mixed value.	function
state	Svelte store, context: {valid: boolean, error: string}.	function

Changes

To see the changes that were made in a given release, please lookup the tag on the releases page. The full changelog could be seen here changelog.md

About

This project is mainly to explore and test Svelte in SPA realm. Any feedback, contribution to this project is welcomed.

The project is in a beta phase, therefore there might be major changes in near future, the annotation should stay the same, though.

Contributing

When contributing to this repository, please first discuss the change you wish to make via issue, email, or any other method with the owners of this repository before making a change.

Pull Request Process

Fork it
Create your feature branch (git checkout -b ft/new-feature-name)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin ft/new-feature-name)
Create new Pull Request

Please make an issue first if the change is likely to increase.

License

Svelte Router is released under the MIT license. See LICENSE.txt.