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>
    var myCaptcha = new jCaptcha({
        el: '.jCaptcha',
        canvas: {
            class: 'jCaptchaCanvas',
            style: {
                // 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.