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A vanilla-JS financial amount input control

Works with
This package works with Browsers
JSR Score
2 months ago (0.0.1)

Travis build status semantic-release

A vanilla-JS financial amount input control. Supports the following features:

  • auto-formatting
  • prevents invalid input whether typed, dragged or pasted
  • 'k', 'm', 'b', etc. multiplier keys

Required Browser Features

The below table lists features that finput requires in order to function properly. If you wish to use finput with a browser that does not support a required feature then using the suggested polyfill may help. Note that there may be more appropriate polyfills than the ones listed.

Required Feature Suggested Polyfill
KeyboardEvent.key keyboardevent-key-polyfill
Symbol babel-polyfill


See an example finput here

Install package

npm install finput

Initialise input

To initialise the finput, simply pass the element and any options into the finput constructor. An object is returned which allows you to interact with the finput API.



Type: Number
Default: 2

Maximum number of decimal digits the value can take


Type: string
Default: ALL

The possible range of values that the value can take

Possible Values:

  • 'ALL': Number can take any value
  • 'POSITIVE': Number can only be positive

Type: Boolean
Default: true
If true, after focus is lost value is formatted to scale number of decimal places


Type: string
Default: ,
The character used to separate thousands in the formatted value. E.g. 1,000


Type: string
Default: .
The character used for the decimal point


Type: Object { character: multiplier }
Default: { 'k': 1000, 'm': 1000000, 'b': 1000000000 }
An object mapping of shortcuts that the user can use to quickly enter common values. E.g. with the default shortcuts, typing k will multiply the number value by 1000


Type: Function(e)
Default: () => {}
A callback function that is fired each time a invalid key is pressed. the callback is called with the KeyboardEvent object that was raised on keydown.


Type: Function(e)
Default: undefined
A callback function that is fired each time the input is focussed. the callback is called with the Event object.

the function used needs to return an object with a start and end value, a numerical representation of the postions to select.

{ start: 0, end: 1 }

setting both values to 0 or failing to return both values will disable selecting functionality


The following properties are exposed on the returned finput instance:


Retrieves the options on the input


Retrieves the raw value of the input (numerical)


Retrieves the formatted value of the input (string)

The following functions are exposed on the returned finput instance:


Sets the options on the input

  • options New options to set. Copied before being set.

Note that setOptions supplements the current options rather than replacing.

element.setOptions({ thousands: '.' });
element.setOptions({ decimal: ',' });

The above therefore results in the following options:

  thousands: '.',
  decimal: ','

Sets the value, fully formatted, for the input

  • val New value to set
  • notNull When true, restricts setting the value if it is null.

Sets and formats the value for the input

  • val New value to set

Removes finputs listeners from the provided element, returning it to a standard native control


Install dependencies:

  • npm install

Adding dependencies:

  • Do not commit yarn.lock
  • Do commit package-lock.json

Run dev server:

  • npm start

Building Library

  • npm run build:dev - Builds a development friendly version of the application
  • npm run build:prod - Builds a minified version of the application
  • npm run compile - Compiles typescript dependency-free version of library

Running tests

Execute the tests locally:

  • npm test

This takes care of doing the following:

  • Updating webdriver server
  • Starting background webdriver server
  • Starting background web server
  • Starting tests
  • Shutting down webdriver server, webserver and tests

The tests can be run for CI using:

  • npm run test:ci

This is the same as npm test but it does not update or start webdriver. We assume that CI/Browserstack takes care of webdriver for us.


semantic-release is used with Travis CI to perform releases on merged PRs to master branch.

Commit messages must follow AngularJS Commit Message Conventions for semantic-release to correctly choose the next version.

If the Travis CI build for a new release is successful, it is published to npm. ./lib/finput.js is used by npm installs, and ./dist/finput.min.js is automatically served by UNPKG CDN at to directly load finput in a browser environment.