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react-json-form-engine

2.0.6 • Public • Published

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Build lightning fast web forms from JSON.

❤️ Conditional logic
❤️ Flexible validation
❤️ Infinite depth
❤️ Rehydratable

While other libraries might utilize react-redux, refs, or Context for form state management, react-json-form-engine relies on React as little as possible, and offloads its core logic to plain JavaScript, while utilzing mobx bindings for rendering. The result is scalable, lightning-fast performance with neglible reliance on the React lifecycle.

It's important to note that this library was designed to manage large, multi-section forms, that may contain conditional logic (e.g. Show field Foo based on the response given in field Bar). This may or may not be for you, but it can also handle simple forms with extreme ease.

It also offers a mechanism for serializing all form responses to JSON for persistence. The reverse also stands, as any form can be easily rehydrated from historical data, and returned to its previous state.


Table of Contents


Live Demo

https://mikechabot.github.io/react-json-form-engine-demo/

https://mikechabot.github.io/react-json-form-engine-storybook/

Installing

Requires React 15.0.0+

$ npm install --save react-json-form-engine

Note: This library renders Bulma semantics; you'll need to import the styles for everything to look nice.

// Import the styles
import 'react-json-form-engine/dist/css/styles.min.css';
 
// Import the API
import { Form, FormEngine } from 'react-json-form-engine';

Storybook

To run the react-json-form-engine storybook locally:

$ git clone https://github.com/mikechabot/react-json-form-engine.git
$ npm install
$ npm run storybook

Available at http://localhost:6006/


Getting Started

First, let's import the API:

import { Form, FormEngine } from 'react-json-form-engine';

Next, we'll need to build a Form Definition, which is the skeleton structure that describes how the form should look and behave. The definition must adhere to a strict schema, and can be represented as a JavaScript object or a JSON Schema. But don't worry about the details yet, we'll get into those.

Once we've built our definition, we'll feed it to the FormEngine, which returns an instance:

const instance = new FormEngine(definition);

To rehydrate a form instance from a previous state, we'd pass in our model as the second argument.

 
const model = {username: 'mikechabot', city: 'Boston', state: 'MA'};
const instance = new FormEngine(definition, model);

Then, we just pass the instance to the <Form /> component, and react-json-form-engine takes care of the rest:

<Form
  instance={instance}
  onUpdate={(id, value) => {}}
  onSubmit={(hasError) => {}}
/>

Login Form Example

Let's create a simple login form. Either follow along below, or check out the Login demo on storybook.

Login Form Definition

Here's our definition, which is a rather simple one. It consists of just a single section with a single subsection, which houses three fields. Note, we're also using a Field Decorator to ensure user_pass renders as a password field:

const loginForm = {
  id: 'loginForm',
  title: 'Welcome to Foo!',
  sections: [
    {
      id: 'loginSection',
      title: 'Login Section',
      subsections: [
        {
          id: 'loginSubsection',
          title: 'Login',
          subtitle: 'Please enter your credentials.',
          fields: [
            {
              id: 'username',
              title: 'Username',
              type: 'string',
              required: true
            },
            {
              id: 'password',
              title: 'Password',
              type: 'string',
              required: true
            },
            {
              id: 'rememberMe',
              title: 'Remember me',
              type: 'boolean'
            }
          ]
        }
      ]
    }
  ],
  decorators: {
    password: {
      component: {
        type: 'password'
      }
    }
  }
};

Now that we have our definition, let's create an instance of FormEngine:

const instance = new FormEngine(loginForm); 

With the instance in hand, we can pass it our <Form /> component:

const LoginForm = () => (
  <Form
    instance={instance}
    onUpdate={(id, value) => {
       // Do stuff
    }}
    onSubmit={hasError => {
       // Do stuff
    }}
  />
);

And once filled out, onSubmit will get us the form responses, and also pass along the state of the form

const LoginForm = () => (
  <Form
    instance={instance}
    onUpdate={(id, value) => {
       // Log the change set
       console.log(`FieldId ${id} was changed to ${value}`);
       
       // Get the full validation results of the field
       console.log(instance.getValidationResultById(id);
       
       // Get just the validation status of the field (i.e. ERROR, OK)
       console.log(instance.getValidationStatusById(id);
    }}
    onSubmit={hasError => {
      if (hasError) {
        // Get form validation results
        console.log(intance.getValidationResults(id)); 
      }
      // Get form responses
      console.log(instance.getModel());               
      
      // Serialize form responses
      console.log(instance.serializeModel());         
    }}
  />
);

Form Engine

Form Definition

Form definitions adhere to a strict schema. They must contain at least one section, which contains at least one subsection, which contains at least one Field Definition. You may find this schema verbose for smaller forms, however its purpose is to scale for significantly complex forms.

View the full schema in the FormAPIService

In forms with a single section, vertical tabs are not displayed. In sections with a single subsection, horizontal tabs are not displayed. See the Layout demos on storybook.

// The most minimal form possible
export default {
  id: <string>,
  title: <string>,
  faIcon: {
      name: <string>,
      prefix: <string>
  },
  sections: [
    {
      id: <string>,
      title: <string>,
      subsections: [
        {
          id: <string>,
          title: <string>,
          fields: [
            {
                ...
            }
          ]
        }
      ]
    }
  ]
};

The faIcon object is optional on the form definition; it supports Font Awesome icons.

Have a look the Simple Form demo on storybook.


Form Definition Validation

Don't worry about making mistakes with your definition. If the FormEngine is instantiated with a malformed definition, the UI will be notified of the failure location.

In the case below, our definition was missing the sections array:

api-check

Have a look at the Malformed Form demo on storybook.


Form Props

Prop Required? Type Description
instance Yes object Created by new FormEngine(definition)
onSubmit Yes func Invoked when Submit is clicked. Is passed with hasError, which is the overall status of the form
onUpdate No func Invoked when the user updates the form. Is passed with the id and value of the field that was updated
submitButtonLabel No string Custom label for the "Submit" button.
hideFormTitle No boolean Hide the form's title
hideFormBorder No boolean Hide the form's border
hideSubsectionTitles No boolean Hide subsection titles. Only applies to sections with a single subsection**
hideSubsectionSubtitles No boolean Hide subsection subtitles
width No number or string Apply a width to the form

** Section titles are only used in multi-section forms, and are used as the label for vertical tabs. Subsection titles are displayed as a heading in sections that contain a single subsection, and as labels for horizontal tabs in sections that are multi-subsection. See the Layout demo on storbyook, and tinker with the prop knobs to see this behavior in action.

Field Definition

Field definitions also adhere to a strict schema. At minimum, they must contain an id, type and title:

// The most minimal field object
{
  id: <string>,       // Uniquely identifies the field within the DOM, and FormEngine instance
  type: <string>,     // Determines the data type of the field response
  title: <string>     // Label of the field
}

Field Type

Determines the data type of the response value stored in the model, and which Default Control to render. To override the default and render an Allowed Control instead, use a Field Decorator.

Note, the info field is the only field type that does not accept input from the end-user; its purpose is to provide a place for the form author to render informational content, such as instructions, to the end-user. This field type utilizes dangerouslySetInnerHTML meaning you're able to render pure HTML. Be aware of XSS concerns.

Field Type Default Control Allowed Controls Supports options?
string <Text /> <Password />, <Textarea />, <Select />, <Radio /> Yes**
boolean <Checkbox /> <Radio /> Yes**
number <Number /> <Range /> No
array <Select /> <Checkboxgroup /> Yes
date <DateTime /> N/A No
info** <section /> N/A No

** Some field types will automatically transition from their Default Control to another Allowed Control if an options array is present in the field definition. (See Field Type Transitions). However, in most cases, you must use a Field Decorator to use another Allowed Control.


Field Children

Any field can contain child fields. Simply create a fields array on the field, and drop in valid Field Definitions. Here's an example of some nested fields, but take a look at the Nesting demo on storybook.

Note: Field children can recurse infinitely, and also be placed on Field Options.

{
  id: 'parent',
  type: 'number',
  title: 'Parent',             
  fields: [
    {
      id: 'child',
      type: 'string',
      title: 'Child',
      fields: [
        {
          id: 'grandchild',
          type: 'number',
          title: 'Grandchild'
        }
      ]
    },
    {
      id: 'child-2',
      type: 'array',
      title: 'Child',
      options: [
        { id: 'op1', title: 'Option 1'},
        { id: 'op2', title: 'Option 2' },
      ]
    }
  ]
}

Have a look at the Nested Fields demo on storybook.


Field Options

Applies to string, boolean, and array field types only.

boolean

Fields of type boolean only accept a maximum of two options; each of which should contain just a title property. The first option is considered the affirmative response:

{
  id: 'my_bool',
  title: 'How often does it occur?',
  type: 'boolean',
  options: [
    { title: 'Always' },
    { title: 'Never' },
  ]
}

string / array

For field types that accept unlimited options (string, array), you must include both an id and title. The ids of the selected option(s) are stored in the model.

{
  id: 'my_arr',
  title: 'Pick some',  
  type: 'array',      // Array type allows for multiple selections
  options: [
    { id: 'op1', title: 'Option 1' },
    { id: 'op2', title: 'Option 2' },
    { id: 'op3', title: 'Option 3' },
  ]
},
{
  id: 'my_str',
  title: 'Pick one',
  type: 'string',    // String type allows for single selection
  options: [
    { id: 'op1', title: 'Option 1' },
    { id: 'op2', title: 'Option 2' },
    { id: 'op3', title: 'Option 3' },
  ]
}

Field Children on Options

For field controls that render selectable options, like <Radio /> or <Checkboxgroup />, you can include Field Children on any of the options. Take a look at the Complex Nesting demo on storybook.

{
  id: 'field_2',
  type: 'string',
  title: 'Select One (Field Type: String)',
  options: [
    {
      id: 'op1',
      title: 'Option 1',
      fields: [{ id: 'explain_1', type: 'string', title: 'Explain' }]
    },
    {
      id: 'op2',
      title: 'Option 2',
      fields: [{ id: 'explain_2', type: 'string', title: 'Explain' }]
    },
    {
      id: 'op3',
      title: 'Option 3',
      fields: [{ id: 'explain_3', type: 'string', title: 'Explain' }]
    }
  ]
}

Field Props

Here's the complete list of props that can be passed to Field Definitions:

Property Type Required Description
id string Yes See Field ID
type string Yes See Field Type
title string Yes Display label for the field
options array No See Field Options
fields array No See Field Children
placeholder string No Placeholder text to display
showCondition object No Condition object (See Conditions)
required boolean No Whether the field is required (See Validation)
pattern string No Pattern to match during validation (See Validation)
min number Yes* Minimum value. (Used for number field types)
max number Yes* Maximum value. (Used for number field types)
showTimeSelect boolean No Only show Date in Date/Time. (Used for date field types)
hideCalendar boolean No Only show Time in Data/Time. (Used for date field types)
content string No Informational content to be displayed to the end-user. Utilizes dangerouslySetInnerHTML. (Used for info field types)

min and max are only required for <Range /> component types.

date field types implement react-datepicker. Any prop that can be passed to react-datepicker can be added to a date field, and it will be passed directly to <Date />, such as timeIntervals, or dateFormat.


Field Type Transitions

string

By default, a string field is rendered as <Text /> (See Field Type), but with options it automatically renders as a <Select />.

{ 
  // Renders as <Text />
  id: 'field_1',
  type: 'string', 
  title: 'Text Field'
},
{             
  // Renders as <Select />
  id: 'field_2',
  type: 'string',
  title: 'Select Field',
  options: [
    { id: "op1", title: "Option 1" },
    { id: "op2", title: "Option 2" },
  ]
}

Have a look at the Strings demo on storybook.


boolean

By default, a boolean field is rendered as <Checkbox /> (See Field Type), but with options it automatically renders as a <Radio />.

{
  id: "field_1",
  type: "boolean",
  title: "Checkbox Field"
},
{
  id: "field_2",
  type: "boolean",
  title: "Radio Field",
  options: [
    { title: "Yes" },
    { title: "No" }
  ]
}

A maximum of two (2) options is allowed for boolean fields. For unlimited <Radio /> options, use the string type with a component of radio.

Have a look at the Booleans demo on storybook.


Field Decorators

Field decorators contain metadata about the fields you've configured in your form definition. Add the decorators object to the root of the Form Definition:

{
  id: 'my_form'
  title: 'My Form',
  sections: [...],
  decorators: {}
}

The decorators object will be keyed by Field ID, and can contain the properties hint and component.


Hint Decorator

Add hint text to any field:

{
  id: "Form_ID",
  title: "Form Title",
  sections: [{
    ...
    subsections: [{
      ...     
      fields: [{
        id: "field_1",
        type: "string",
        title: "Field title"
      }]
    }]
  }],
  decorators: {
    field_1: {
      hint: "This is some hint text!"   // Add hint text to any field
    }
  }
}

Component Decorator

Every field type renders a Default Control (See Field Type), however you'll often want to explicitly override the default component type in favor of another. In some cases, this occurs automatically (See Field Type Transitions), however most times you'll need to specify a component decorator.

Let's update field_1 from a <Select /> to a <Checkboxgroup />:

{
  id: "Form_ID",
  title: "Form Title",
  sections: [{
    ...
    subsections: [{
      ...     
      fields: [{
        id: "field_1",
        type: "array",
        title: "Field title",
        options: [
           ...
        ]
      }]
    }]
  }],
  decorators: {
    field_1: {
      hint: 'More hint text!',
      component: {
        type: 'checkboxgroup'   // Override the default component type
      }
    }
  }
}

Here's a list of field types with overrideable components:

Field Type Component Decorator Overrides
string password, textarea, radio
number range
array checkboxgroup

Take a look at a component override in the Arrays demo.


Serialize

Easily serialize the form's responses by calling serializeModel on the instance:

const json = instance.serializeModel();

To access the model without serialization, use the below:

const map = instance.getModel();           // {fooId: 'bar', bazId: 'qux'}
const array = instance.getModelAsArray();  // [{fooId: 'bar'}, {bazId: 'qux'}]

Validation

Three types of validation are supported:

Type Supported Data Types
Required All
Numeric (min/max) number
Regular Expression string, number

Take a look at the Validation demos on storybook.


Required

Add required: true to any field definition:

{
  id: 'username',
  type: 'string',
  title: 'Username',
  required: true
},
{
  id: 'myOptions',
  type: 'array',
  title: 'Option Group',
  required: true,
  options: [
    { id: 'op1', title: 'Option 1' },
    { id: 'op2', title: 'Option 2' },
    { id: 'op3', title: 'Option 3' },
    { id: 'op4', title: 'Option 4' }
  ]
}

Note: Fields are only validated if they are visible in the DOM. For instance, if a field's showCondition (See Conditions) is not met, it will not be displayed to the end-user; conditionally hidden fields are not validated.

Take a look at the Required Validation demo in storybook.


Numeric

Add min: <number> or max: <number> or both to any number type field:

{
  id: 'age',
  type: 'number',
  title: 'Age',
  min: 0,
  max: 120
}

Note min/max values are only validated once the field is marked as dirty, that is, the user inputs a value.

Take a look at the Numeric Validation demo on storybook.


Regular Expression

Add pattern: <regex> to any string or number field:

{
  id: 'myRegEx',
  type: 'string',
  title: 'My Field',
  pattern: '^foobar$',
}

Take a look at the Regex Demo on storybook.


Multiple Validators

Validators can be combined. The following number field will only pass validation if the following conditions are met:

  1. The value is not undefined, per required.
  2. The value is greater-than or equal to zero, per min.
  3. The value is less-than or equal to 300, per max.
  4. The value starts with the numeral 3, per pattern.
{
  id: 'num1',
  type: 'number',
  title: 'Number Regex',
  pattern: '^3',
  required: true,
  min: 0,
  max: 300
}

Conditions

Conditionally show any field by giving it a showCondition. Take a look at the Conditions demos before moving on.

{
  id: 'myString',
  type: 'string',
  title: 'Conditional Field',
  showCondition: {...}
}

A showCondition contains a type and one or more expressions, which also contain a type. Expressions are evaluated against one another, or the form model itself to conditionally show a field (e.g. Show field Foo based on the response given in field Bar).

Note: showConditions also accept a not property, and if set to true, the condition will be negated.

Condition Types

Type Data Types Description
BETWEEN number Determine if a FORM_RESPONSE is between a CONST value
BLANK string, array, date Determine if a FORM_RESPONSE is blank**
CONTAINS array Determine if a FORM_RESPONSE contains a CONST value
EMPTY string, array, date Determine if a FORM_RESPONSE is empty***
EQUAL string number, date, boolean Determine if a FORM_RESPONSE is equal to a CONST
GREATER_THAN number Determine if a FORM_RESPONSE is greater than a CONST
LESS_THAN number Determine if a FORM_RESPONSE is less than a CONST

** BLANK is defined as an empty array or string, undefined, or null.

*** EMPTY implements Lodash's isEmpty

Expression Types

Type Uses
CONST A constant value
FORM_RESPONSE References a field id in the form instance

showConditions are evaluated every time the form is updated.


Condition Examples

Take a look at the Conditions demos for live examples.

CONTAINS Example

The following checkboxgroup has three option fields. The second option has a child field; if this option is selected, a string field is rendered underneath it.

Have a look at the field definition below, and then we'll walk through it.

{
  id: 'myArray',
  type: 'array',
  title: 'Select some options to display the children',
  options: [
    {
      id: 'option1',
      title: 'Option 1'
    },
    {
      id: 'option2',
      title: 'Option 2',
      fields: [
        {
          id: 'myString',
          type: 'string',
          title: 'Conditional Field',
          showCondition: {
            type: 'CONTAINS',
            expressions: [
              {
                type: 'FORM_RESPONSE',
                id: 'myArray'
              },
              {
                type: 'CONST',
                value: 'option2'
              }
            ]
          }
        }
      ]
    },
    {
      id: 'option3',
      title: 'Option 3',
    }  
  ]
}

The showCondition on the myString field can appear cryptic, but let's take a closer look at it:

showCondition: {
  type: 'CONTAINS',
  expressions: [
    {
      type: 'FORM_RESPONSE',
      id: 'myArray'
    },
    {
      type: 'CONST',
      value: 'option2'
    }
  ]
}

The condition is of type CONTAINS, and contains an array of expressions.

  • One expression is of type FORM_RESPONSE and references by id the field myArray.
  • One expression is of type CONST, and contains the value option2.

The expression-service will pull the value of myArray from the instance, and determine if the CONST value of option2 is contained within in. If so, myString will be displayed.

At its core, this showCondition says "Show myString if the user selected option2 in the myArray field."

If the user selects all three options for myArray, its form response value in the instance would be ["option1", "option2", "option3"], therefore myString would be shown since the value in the CONST expression (option2) is contained within the the form response.


EMPTY Example

Let's take a look at an EMPTY example. We'll use the same checkboxgroup field from the condition example above, however in this case, the conditional field (myNumber) won't be rendered under an option field, but rather under the entire field itself regardless of which option is selected.

Have a look at the field definition below, and then we'll walk through it.

{
  id: 'myArray',
  type: 'array',
  title: 'Select some options to display the children',
  options: [
    {
      id: 'option1',
      title: 'Option 1'
    },
    {
      id: 'option2',
      title: 'Option 2',
    },
    {
      id: 'option3',
      title: 'Option 3',
    },
  ],
  fields: [
    {
      id: 'myNumber',
      type: 'number',
      title: 'Number Field',
      showCondition: {
        type: 'EMPTY',
        not: true,
        expression: {
            type: 'FORM_RESPONSE',
            id: 'myArray'
        }
      }
    }
  ]
}

Let's pull out the showCondition and take a closer look:

showCondition: {
  type: 'EMPTY',
  not: true,
  expression: {
      type: 'FORM_RESPONSE',
      id: 'myArray'
  }
}

The condition is of type EMPTY, contains a single expression, and also the not flag for negation.

  • The expression is of type FORM_RESPONSE and references by id the field myArray.
  • The not flag will negate the EMPTY condition being evaluated.

The expression-service will pull the value of myArray from the instance, and determine if it is not empty. If so, the myNumber field will be displayed.

At its core, this expression says "Show myNumber if the user selected any of the options in myArray"

Conversely, if the not flag was removed from the condition, the myNumber field would immediately display to the user, but would be conditionally hidden if the user selected any of the options in myArray.


GREATER_THAN Example

Let's take a look at a GREATER_THAN example. The number field below (myNumber) has a single conditional child field, which will be displayed based based on the value input into myNumber.

Have a look at the field definition below, and then we'll walk through it.

{
  id: 'myNumber',
  type: 'number',
  title: 'Greater-Than (>)',
  min: 0,
  max: 10,
  fields: [
    {
      id: 'myString',
      type: 'string',
      title: 'Field',
      showCondition: {
        type: 'GREATER_THAN',
        expressions: [
          {
            type: 'FORM_RESPONSE',
            id: 'myNumber'
          },
          {
            type: 'CONST',
            value: 5
          }
        ]
      }
    }
  ]
}

Let's pull out the showCondition and take a closer look:

showCondition: {
  type: 'GREATER_THAN',
  expressions: [
    {
      type: 'FORM_RESPONSE',
      id: 'myNumber'
    },
    {
      type: 'CONST',
      value: 5
    }
  ]
}

The condition is of type GREATER_THAN, and contains an array of expressions.

  • One expression is of type FORM_RESPONSE and references by id the field myNumber.
  • One expression is of type CONST, and contains the value 5.

The expression-service will pull the value of myNumber from the instance, and determine if it is greater than 5. If so, the myString field will be displayed.

At its core, this expression says "Show myString if myNumber is greater than 5."


BETWEEN Condition Example

Let's take a look at a BETWEEN example. The following range field (myNumber) has a min/max of 0 and 100 respectively, and also contains a single conditional child field, which will be displayed when the value of myNumber is between 25 and 75.

{
  id: 'myNumber',
  type: 'number',
  title: 'Between 25 and 75',
  min: 0,
  max: 100,
  fields: [
    {
      id: 'myString',
      type: 'string',
      title: 'Field',
      showCondition: {
        type: 'BETWEEN',
        expressions: [
          {
            type: 'FORM_RESPONSE',
            id: 'myNumber'
          },
          {
            type: 'CONST',
            value: [25, 75]
          }
        ]
      }
    }
  ]
}

Let's pull out the showCondition and take a closer look:

showCondition: {
  type: 'BETWEEN',
  expressions: [
    {
      type: 'FORM_RESPONSE',
      id: 'myNumber'
    },
    {
      type: 'CONST',
      value: [25, 75]
    }
  ]
}

The condition is of type BETWEEN, and contains an array of expressions.

  • One expression is of type FORM_RESPONSE and references by id the field myNumber.
  • One expression is of type CONST, and contains an array of values.

The expression-service will pull the value of myNumber from the instance, and determine if it is between 25 and 75. If so, the myString field will be displayed.

At its core, this expression says "Show myString if myNumber is between 25 and 75."

Note that the CONST array on BETWEEN condition types requires a length of two (2); the condition will not be evaluted otherwise.

Install

npm i react-json-form-engine

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2.0.6

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