JavaScript Captcha

Simple captcha component (<2KB) written in pure JavaScript with no dependencies

Simple numeric captcha rendered within basic canvas element.

Demo

Demo can be seen here.

Install

npm install js-captcha --save

Usage

Just include required JavaScript:

<script src="jCaptcha.js"></script>

or

import jCaptcha from 'jCaptcha';

Define main captcha input element in HTML:

<input class="jCaptcha" type="text" placeholder="Type in result please">

Initialize it:

<script>
    let myCaptcha = new jCaptcha({
        el: '.jCaptcha',
        canvasClass: 'jCaptchaCanvas',
        canvasStyle: {
            // required properties for captcha stylings:
            width: 100,
            height: 15,
            textBaseline: 'top',
            font: '15px Arial',
            textAlign: 'left',
            fillStyle: '#ddd'
        },
        // set callback function for success and error messages:
        callback: ( response, $captchaInputElement, numberOfTries ) => {
            if ( response == 'success' ) {
                // success handle, e.g. continue with form submit
            }
            if ( response == 'error' ) {
                // error handle, e.g. add error class to captcha input

                if (numberOfTries === 3) {
                    // maximum attempts handle, e.g. disable form
                }
            }
        }
    });
</script>

And then call validate() method when required (e.g. on form submit event):

<script>
    myCaptcha.validate();
</script>

No stylings included, just style it as you wish, see options below.

Options

jCaptcha can take an optional parameter - an [Object] of key/value settings:

Name	Required	Type	Default	Description
el	false	[String]	'jCaptcha'	CSS class for input element
requiredValue	false	[String]	'*'	Render new random numbers on error validate
resetOnError	false	[Boolean]	true	Mandatory field indicator
focusOnError	false	[Boolean]	true	Focus input field on error validate
clearOnSubmit	false	[Boolean]	true'	Clear input value on every validate
callback	false	[Function]	null	As invoked function these useful arguments are returned: response (type: String, value: 'success' or 'error'), captcha (type: Element) and number of tries (type: Number)
canvasClass	false	[String]	'jCaptchaCanvas'	CSS class of canvas captcha
canvasStyle	true	[Object]	{}	Canvas stylings object, required for canvas appearance
canvasStyle.width	false	[Number]	null	Width of canvas captcha element (in px)
canvasStyle.height	false	[Number]	null	Height of canvas captcha element (in px)
canvasStyle.font	false	[String]	''	Font size and font family of canvas captcha element
canvasStyle.fillStyle	false	[String]	''	Text color of canvas captcha element
canvasStyle.textAlign	false	[String]	''	Text align of canvas captcha element
canvasStyle.textBaseline	false	[String]	''	Text baseline of canvas captcha element

API

reset() - generate and render new random numbers

validate() - validate entered result in input field

Browser support

Works in every modern browser which has support for canvas element.

License

js-captcha is licensed under the MIT license.