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Detect if the browser is running in Private mode (Promise based)
// uncomment if you are transpiling with Babel + Webpack
// const { window, document } = global;
/**
* Lightweight script to detect whether the browser is running in Private mode.
* @returns {Promise}
*
* Live demo:
* @see http://live.datatables.net/piduzelo/1
*
* This snippet uses ES2015 syntax. If you want to run it in old browsers, transpile it with Babel:
* @see https://babeljs.io/repl
*
* This snippet uses Promises. If you want to run it in old browsers, polyfill it:
* @see https://cdn.jsdelivr.net/npm/es6-promise@4/dist/es6-promise.auto.min.js
*
* More Promise Polyfills:
* @see https://ourcodeworld.com/articles/read/316/top-5-best-javascript-promises-polyfills
*/
function isPrivateMode() {
return new Promise((resolve) => {
const yes = () => resolve(true); // is in private mode
const not = () => resolve(false); // not in private mode
const testLocalStorage = () => {
try {
if (localStorage.length) not();
else {
localStorage.x = 1;
localStorage.removeItem('x');
not();
}
} catch (e) {
// Safari only enables cookie in private mode
// if cookie is disabled, then all client side storage is disabled
// if all client side storage is disabled, then there is no point
// in using private mode
navigator.cookieEnabled ? yes() : not();
}
};
// Chrome & Opera adjusted to cope with this issue
//https://stackoverflow.com/questions/2860879/detecting-if-a-browser-is-using-private-browsing-mode#targetText=Google%20is%20removing%20the%20ability,permanently%20in%20Chrome%2076%20onwards.&targetText=To%20anyone%20else%20coming%20across,mode%20through%20Javascript%20or%20CSS.
var fs = window.webkitRequestFileSystem || window.RequestFileSystem;
if (fs) {
async function f() {
if ('storage' in navigator && 'estimate' in navigator.storage) {
const {
usage,
quota
} = await navigator.storage.estimate();
if (quota < 120000000) {
return yes();
} else {
return not();
}
}
}
return void f();
}
// Firefox
if ('MozAppearance' in document.documentElement.style) {
if (indexedDB === null) return yes();
const db = indexedDB.open('test');
db.onerror = yes;
db.onsuccess = not;
return void 0;
}
// Safari
const isSafari = navigator.userAgent.match(/Version\/([0-9\._]+).*Safari/);
if (isSafari) {
const version = parseInt(isSafari[1], 10);
if (version < 11) return testLocalStorage();
try {
window.openDatabase(null, null, null, null);
return not();
} catch (_) {
return yes();
}
}
// IE10+ & Edge InPrivate
if (!window.indexedDB && (window.PointerEvent || window.MSPointerEvent)) {
return yes();
}
// default navigation mode
return not();
});
}
isPrivateMode().then(function (isPrivate) {
console.log('Browsing in private mode? ', isPrivate);
});
@cjies
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cjies commented Aug 29, 2019

found a bug in line 54, if the site is serving with HTTP protocol, navigator.storage API will not exist.
Not sure how to fix it

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