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/**
* http://schalkneethling.github.io/blog/2015/11/06/respect-user-choice-do-not-track/
* https://github.com/schalkneethling/dnt-helper/blob/master/js/dnt-helper.js
*
* Returns true or false based on whether doNotTack is enabled. It also takes into account the
* anomalies, such as !bugzilla 887703, which effect versions of Fx 31 and lower. It also handles
* IE versions on Windows 7, 8 and 8.1, where the DNT implementation does not honor the spec.
* @see https://bugzilla.mozilla.org/show_bug.cgi?id=1217896 for more details
* @params {string} [dnt] - An optional mock doNotTrack string to ease unit testing.
* @params {string} [userAgent] - An optional mock userAgent string to ease unit testing.
* @returns {boolean} true if enabled else false
*/
function _dntEnabled(dnt, userAgent) {
'use strict';
// for old version of IE we need to use the msDoNotTrack property of navigator
// on newer versions, and newer platforms, this is doNotTrack but, on the window object
// Safari also exposes the property on the window object.
var dntStatus = dnt || navigator.doNotTrack || window.doNotTrack || navigator.msDoNotTrack;
var ua = userAgent || navigator.userAgent;
// List of Windows versions known to not implement DNT according to the standard.
var anomalousWinVersions = ['Windows NT 6.1', 'Windows NT 6.2', 'Windows NT 6.3'];
var fxMatch = ua.match(/Firefox\/(\d+)/);
var ieRegEx = /MSIE|Trident/i;
var isIE = ieRegEx.test(ua);
// Matches from Windows up to the first occurrence of ; un-greedily
// http://www.regexr.com/3c2el
var platform = ua.match(/Windows.+?(?=;)/g);
// With old versions of IE, DNT did not exist so we simply return false;
if (isIE && typeof Array.prototype.indexOf !== 'function') {
return false;
} else if (fxMatch && parseInt(fxMatch[1], 10) < 32) {
// Can't say for sure if it is 1 or 0, due to Fx bug 887703
dntStatus = 'Unspecified';
} else if (isIE && platform && anomalousWinVersions.indexOf(platform.toString()) !== -1) {
// default is on, which does not honor the specification
dntStatus = 'Unspecified';
} else {
// sets dntStatus to Disabled or Enabled based on the value returned by the browser.
// If dntStatus is undefined, it will be set to Unspecified
dntStatus = { '0': 'Disabled', '1': 'Enabled' }[dntStatus] || 'Unspecified';
}
return dntStatus === 'Enabled' ? true : false;
}