ie-emulation-modes-warning.js 2.0 KB
// NOTICE!! DO NOT USE ANY OF THIS JAVASCRIPT
// IT'S JUST JUNK FOR OUR DOCS!
// ++++++++++++++++++++++++++++++++++++++++++
/*!
 * Copyright 2014-2015 Twitter, Inc.
 *
 * Licensed under the Creative Commons Attribution 3.0 Unported License. For
 * details, see https://creativecommons.org/licenses/by/3.0/.
 */
// Intended to prevent false-positive bug reports about Bootstrap not working properly in old versions of IE due to folks testing using IE's unreliable emulation modes.
(function () {
	'use strict';

	function emulatedIEMajorVersion() {
		var groups = /MSIE ([0-9.]+)/.exec(window.navigator.userAgent)
		if (groups === null) {
			return null
		}
		var ieVersionNum = parseInt(groups[1], 10);
		return Math.floor(ieVersionNum);
	}

	function actualNonEmulatedIEMajorVersion() {
		// Detects the actual version of IE in use, even if it's in an older-IE emulation mode.
		// IE JavaScript conditional compilation docs: https://msdn.microsoft.com/library/121hztk3%28v=vs.94%29.aspx
		// @cc_on docs: https://msdn.microsoft.com/library/8ka90k2e%28v=vs.94%29.aspx
		var jscriptVersion = new Function('/*@cc_on return @_jscript_version; @*/')() // jshint ignore:line
		if (jscriptVersion === undefined) {
			return 11; // IE11+ not in emulation mode
		}
		if (jscriptVersion < 9) {
			return 8; // IE8 (or lower; haven't tested on IE<8)
		}
		return jscriptVersion; // IE9 or IE10 in any mode, or IE11 in non-IE11 mode
	}

	var ua = window.navigator.userAgent
	if (ua.indexOf('Opera') > -1 || ua.indexOf('Presto') > -1) {
		return; // Opera, which might pretend to be IE
	}
	var emulated = emulatedIEMajorVersion()
	if (emulated === null) {
		return; // Not IE
	}
	var nonEmulated = actualNonEmulatedIEMajorVersion()

	if (emulated !== nonEmulated) {
		window.alert('WARNING: You appear to be using IE' + nonEmulated + ' in IE' + emulated + ' emulation mode.\nIE emulation modes can behave significantly differently from ACTUAL older versions of IE.\nPLEASE DON\'T FILE BOOTSTRAP BUGS based on testing in IE emulation modes!')
	}
})();