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This article mainly explains "how to use pure JavaScript to generate pictures or slider CAPTCHA function", the content of the article is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in depth, together to study and learn "how to use pure JavaScript to generate pictures or slider CAPTCHA function" it!

Captchapng

CAPTCHA generation module realized by pure JavaScript.

Easy to install and less dependent:

Npm install captchapng

Example:

Var captchapng = require ('captchapng'); app.get (' / sign/captcha.png', function (req, res) {var captchaNumber = parseInt (Math.random () * 9000 + 1000) req.session.captcha = captchaNumbervar p = new captchapng (80 mine20, captchaNumber); / / width,height,numeric captchap.color (0,0,0,0); / / First color: background (red, green, blue, alpha) p.color (80,80,80,255) / / Second color: paint (red, green, blue, alpha) var img = p.getBase64 (); var imgbase64 = new Buffer (img,'base64'); res.writeHead (200,{ 'Content-Type':' image/png'}); res.end (imgbase64);})

Express + Captcha

CAPTCHA generation module designed for Express framework.

Installation & example:

$npm install captchaUsage (for Express 4) 'use strict'const express = require (' express') const session = require ('express-session') const bodyParser = require (' body-parser') const captchaUrl ='/ captcha.jpg'const captchaId = 'captcha'const captchaFieldName =' captcha'const captcha = require ('. / captcha'). Create ({cookie: captchaId}) const app = express () app.use (session ({secret: 'keyboard cat',resave: false,saveUninitialized: true) }) app.use (bodyParser.urlencoded ({extended: false})) app.get (captchaUrl, captcha.image ()) app.get ('/', (req, res) = > {res.type ('html') res.end (`

`)}) app.post ('/ login', (req, res) = > {res.type ('html') res.end (`

CAPTCHA VALID: ${captcha.check (req, req.body [captchaFieldName])}

`)}) app.listen (8080, () = > {console.log ('server started')})

Front-end slider verification

The front-end generation track is sent to the back-end verification, the input is simple, but it is easy to crack.

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