常用浏览器环境判断

 var inWeex = typeof WXEnvironment !== 'undefined' && !!WXEnvironment.platform;
 var weexPlatform = inWeex && WXEnvironment.platform.toLowerCase();
 var UA = inBrowser && window.navigator.userAgent.toLowerCase();
 var isIE = UA && /msie|trident/.test(UA);
 var isIE9 = UA && UA.indexOf('msie 9.0') > 0;
 var isEdge = UA && UA.indexOf('edge/') > 0;
 var isAndroid = (UA && UA.indexOf('android') > 0) || (weexPlatform === 'android');
 var isIOS = (UA && /iphone|ipad|ipod|ios/.test(UA)) || (weexPlatform === 'ios');
 var isChrome = UA && /chrome\/\d+/.test(UA) && !isEdge;
 var isPhantomJS = UA && /phantomjs/.test(UA);
 var isFF = UA && UA.match(/firefox\/(\d+)/);