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Detect private browsing mode (InPrivate Browsing or Incognito).
function retry(isDone, next) {
var current_trial = 0, max_retry = 50, interval = 10, is_timeout = false;
var id = window.setInterval(
function() {
if (isDone()) {
window.clearInterval(id);
next(is_timeout);
}
if (current_trial++ > max_retry) {
window.clearInterval(id);
is_timeout = true;
next(is_timeout);
}
},
10
);
}
function isIE10OrLater(user_agent) {
var ua = user_agent.toLowerCase();
if (ua.indexOf('msie') === 0 && ua.indexOf('trident') === 0) {
return false;
}
var match = /(?:msie|rv:)\s?([\d\.]+)/.exec(ua);
if (match && parseInt(match[1], 10) >= 10) {
return true;
}
return false;
}
function detectPrivateMode(callback) {
var is_private;
if (window.webkitRequestFileSystem) {
window.webkitRequestFileSystem(
window.TEMPORARY, 1,
function() {
is_private = false;
},
function(e) {
console.log(e);
is_private = true;
}
);
} else if (window.indexedDB && /Firefox/.test(window.navigator.userAgent)) {
var db;
try {
db = window.indexedDB.open('test');
} catch(e) {
is_private = true;
}
if (typeof is_private === 'undefined') {
retry(
function isDone() {
return db.readyState === 'done' ? true : false;
},
function next(is_timeout) {
if (!is_timeout) {
is_private = db.result ? false : true;
}
}
);
}
} else if (isIE10OrLater(window.navigator.userAgent)) {
is_private = false;
try {
if (!window.indexedDB) {
is_private = true;
}
} catch (e) {
is_private = true;
}
} else if (window.localStorage && /Safari/.test(window.navigator.userAgent)) {
try {
window.localStorage.setItem('test', 1);
} catch(e) {
is_private = true;
}
if (typeof is_private === 'undefined') {
is_private = false;
window.localStorage.removeItem('test');
}
}
retry(
function isDone() {
return typeof is_private !== 'undefined' ? true : false;
},
function next(is_timeout) {
callback(is_private);
}
);
}
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
</head>
<body>
<div id="result"></div>
<script src="detect-private-browsing.js"></script>
<script>
detectPrivateMode(
function(is_private) {
document.getElementById('result').innerHTML = typeof is_private === 'undefined' ? 'cannot detect' : is_private ? 'private' : 'not private';
}
);
</script>
</body>
</html>
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