@mona-health/react-input-mask

Input masking component for React. Made with attention to UX.

Demo

Table of Contents

• Installation
• Usage
• Properties
• Known Issues

Installation

npm install --save @mona-health/react-input-mask

react-input-mask v3 requires React 16.8.0 or later. If you need support for older versions, use version 2.

Usage

import React from "react";
import InputMask from "@mona-health/react-input-mask";

function DateInput(props) {
  return (
    <InputMask
      mask="99/99/9999"
      onChange={props.onChange}
      value={props.value}
    />
  );
}

Properties

Name	Type	Default	Description
mask	{String|Array<String, RegExp>}		Mask format
maskPlaceholder	{String}	_	Placeholder to cover unfilled parts of the mask
alwaysShowMask	{Boolean}	false	Whether mask prefix and placeholder should be displayed when input is empty and has no focus
beforeMaskedStateChange	{Function}		Function to modify value and selection before applying mask
children	{ReactElement}		Custom render function for integration with other input components

mask

Mask format. Can be either a string or array of characters and regular expressions.

<InputMask mask="99/99/99" />

Simple masks can be defined as strings. The following characters will define mask format:

Character	Allowed input
9	0-9
a	a-z, A-Z
*	0-9, a-z, A-Z

Any format character can be escaped with a backslash.

More complex masks can be defined as an array of regular expressions and constant characters.

// Canadian postal code mask
const firstLetter = /(?!.*[DFIOQU])[A-VXY]/i;
const letter = /(?!.*[DFIOQU])[A-Z]/i;
const digit = /[0-9]/;
const mask = [firstLetter, digit, letter, " ", digit, letter, digit];
return <InputMask mask={mask} />;

maskPlaceholder

// Will be rendered as 12/--/--
<InputMask mask="99/99/99" maskPlaceholder="-" value="12" />

// Will be rendered as 12/mm/yy
<InputMask mask="99/99/99" maskPlaceholder="dd/mm/yy" value="12" />

// Will be rendered as 12/
<InputMask mask="99/99/99" maskPlaceholder={null} value="12" />

Character or string to cover unfilled parts of the mask. Default character is "_". If set to null or empty string, unfilled parts will be empty as in a regular input.

alwaysShowMask

If enabled, mask prefix and placeholder will be displayed even when input is empty and has no focus.

beforeMaskedStateChange

In case you need to customize masking behavior, you can provide beforeMaskedStateChange function to change masked value and cursor position before it's applied to the input.

It receieves an object with previousState, currentState and nextState properties. Each state is an object with value and selection properites where value is a string and selection is an object containing start and end positions of the selection.

1. previousState: Input state before change. Only defined on change event.
2. currentState: Current raw input state. Not defined during component render.
3. nextState: Input state with applied mask. Contains value and selection fields.

Selection positions will be null if input isn't focused and during rendering.

beforeMaskedStateChange must return a new state with value and selection.

// Trim trailing slashes
function beforeMaskedStateChange({ nextState }) {
  let { value } = nextState;
  if (value.endsWith("/")) {
    value = value.slice(0, -1);
  }

  return {
    ...nextState,
    value,
  };
}

return (
  <InputMask
    mask="99/99/99"
    maskPlaceholder={null}
    beforeMaskedStateChange={beforeMaskedStateChange}
  />
);

Please note that beforeMaskedStateChange executes more often than onChange and must be pure.

children

To use another component instead of regular <input /> provide it as children. The following properties, if used, should always be defined on the InputMask component itself: onChange, onMouseDown, onFocus, onBlur, value, disabled, readOnly.

import React from "react";
import InputMask from "@mona-health/react-input-mask";
import MaterialInput from "@material-ui/core/Input";

// Will work fine
function Input(props) {
  return (
    <InputMask mask="99/99/9999" value={props.value} onChange={props.onChange}>
      <MaterialInput type="tel" disableUnderline />
    </InputMask>
  );
}

// Will throw an error because InputMask's and children's onChange props aren't the same
function InvalidInput(props) {
  return (
    <InputMask mask="99/99/9999" value={props.value}>
      <MaterialInput type="tel" disableUnderline onChange={props.onChange} />
    </InputMask>
  );
}

Caveat: To support both class and function component children InputMask used to use ReactDOM.findDOMNode, which is now deprecated. To handle removing this, direct child class components are no longer supported. The children component is now either:

1. a function component that implments React.forwardRef

   const FunctionalInputComponent = React.forwardRef((props, ref) => {
     return <input ref={ref} {...props} />;
   });

2. a class component that is wrapped in a function component that implements React.forwardRef (innerRef can be called anything as long as it's not ref)

   class InnerClassInputComponent extends React.Component {
     render() {
       const { innerRef, ...restProps } = this.props;
       return (
         <div>
           <input ref={innerRef} {...restProps} />
         </div>
       );
     }
   }
   
   const ClassInputComponent = React.forwardRef((props, ref) => {
     return <InnerClassInputComponent innerRef={ref} {...props} />;
   });

For more information see the Material UI Composition guide - caveat with Refs.

Known Issues

Autofill

Browser's autofill requires either empty value in input or value which exactly matches beginning of the autofilled value. I.e. autofilled value "[phone]" will work with "+1" or "+1 (5", but won't work with "+1 (___) ___-____" or "1 (555)". There are several possible solutions:

1. Set maskPlaceholder to null and trim space after "+1" with beforeMaskedStateChange if no more digits are entered.
2. Apply mask only if value is not empty. In general, this is the most reliable solution because we can't be sure about formatting in autofilled value.
3. Use less formatting in the mask.

Please note that it might lead to worse user experience (should I enter +1 if input is empty?). You should choose what's more important to your users — smooth typing experience or autofill. Phone and ZIP code inputs are very likely to be autofilled and it's a good idea to care about it, while security confirmation code in two-factor authorization shouldn't care about autofill at all.

Cypress tests

The following sequence could fail

cy.get("input").focus().type("12345").should("have.value", "12/34/5___"); // expected <input> to have value 12/34/5___, but the value was 23/45/____

Since focus is not an action command, it behaves differently than the real user interaction and, therefore, less reliable.

There is a few possible workarounds

// Start typing without calling focus() explicitly.
// type() is an action command and focuses input anyway
cy.get("input").type("12345").should("have.value", "12/34/5___");

// Use click() instead of focus()
cy.get("input").click().type("12345").should("have.value", "12/34/5___");

// Or wait a little after focus()
cy.get("input")
  .focus()
  .wait(50)
  .type("12345")
  .should("have.value", "12/34/5___");

Building

Running npm install runs lint, test, clean, types and build scripts too.

Set the CHROME_BIN environment variable which is the path to the Chrome binary to prevent karma errors in npm run test.

Thanks

Thanks to BrowserStack for the help with testing on real devices