Counting unique visitors and bounces without cookies.
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const express = require('express') | |
const app = express() | |
app.get('/ping', (req, res) => { | |
const now = Date.now(), | |
day = 8.64e7 | |
// calculate midnight today and tomorrow | |
const midnight = Math.floor(now / day) * day | |
const midnightDate = new Date(midnight) | |
const midnightTomorrow = Math.ceil(now / day) * day | |
// get the if-modified-since header or default to midnight | |
const modified = req.headers['if-modified-since'] | |
let date = modified ? new Date(modified) : midnightDate | |
// is the date less than today? set it to today | |
date = date - midnightDate < 0 ? midnightDate : date | |
// add 1 second to the date | |
date.setSeconds(date.getSeconds() + 1) | |
// calculate a visit count | |
const counter = (date - new Date(midnight)) / 1000 - 1 | |
// set a max age | |
const maxAge = Math.round((midnightTomorrow - now) / 1000) | |
res.set('Cache-Control', `public, max-age=${maxAge}, no-cache`) | |
// set last-modified header | |
res.set('Last-Modified', date.toGMTString()) | |
// remove the etag | |
res.set('etag', false) | |
// return the count as a string | |
res.send(String(counter)) | |
}) | |
app.listen(3001, () => console.log(`Counter launched on 3001`)) |
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View a demo of this here 👉 https://lastmodified.normally.com/
And read more about it here: Privacy-preserving analytics: How we count unique visitors without cookies, UIDs or fingerprinting.