echarts源码中关于 判断平台的有用代码

function detect(ua) {
    var os = {};
    var browser = {};
    // var webkit = ua.match(/Web[kK]it[\/]{0,1}([\d.]+)/);
    // var android = ua.match(/(Android);?[\s\/]+([\d.]+)?/);
    // var ipad = ua.match(/(iPad).*OS\s([\d_]+)/);
    // var ipod = ua.match(/(iPod)(.*OS\s([\d_]+))?/);
    // var iphone = !ipad && ua.match(/(iPhone\sOS)\s([\d_]+)/);
    // var webos = ua.match(/(webOS|hpwOS)[\s\/]([\d.]+)/);
    // var touchpad = webos && ua.match(/TouchPad/);
    // var kindle = ua.match(/Kindle\/([\d.]+)/);
    // var silk = ua.match(/Silk\/([\d._]+)/);
    // var blackberry = ua.match(/(BlackBerry).*Version\/([\d.]+)/);
    // var bb10 = ua.match(/(BB10).*Version\/([\d.]+)/);
    // var rimtabletos = ua.match(/(RIM\sTablet\sOS)\s([\d.]+)/);
    // var playbook = ua.match(/PlayBook/);
    // var chrome = ua.match(/Chrome\/([\d.]+)/) || ua.match(/CriOS\/([\d.]+)/);
    var firefox = ua.match(/Firefox\/([\d.]+)/);
    // var safari = webkit && ua.match(/Mobile\//) && !chrome;
    // var webview = ua.match(/(iPhone|iPod|iPad).*AppleWebKit(?!.*Safari)/) && !chrome;
    var ie = ua.match(/MSIE\s([\d.]+)/)
        // IE 11 Trident/7.0; rv:11.0
        || ua.match(/Trident\/.+?rv:(([\d.]+))/);
    var edge = ua.match(/Edge\/([\d.]+)/); // IE 12 and 12+

    var weChat = (/micromessenger/i).test(ua);

    // Todo: clean this up with a better OS/browser seperation:
    // - discern (more) between multiple browsers on android
    // - decide if kindle fire in silk mode is android or not
    // - Firefox on Android doesn't specify the Android version
    // - possibly devide in os, device and browser hashes

    // if (browser.webkit = !!webkit) browser.version = webkit[1];

    // if (android) os.android = true, os.version = android[2];
    // if (iphone && !ipod) os.ios = os.iphone = true, os.version = iphone[2].replace(/_/g, '.');
    // if (ipad) os.ios = os.ipad = true, os.version = ipad[2].replace(/_/g, '.');
    // if (ipod) os.ios = os.ipod = true, os.version = ipod[3] ? ipod[3].replace(/_/g, '.') : null;
    // if (webos) os.webos = true, os.version = webos[2];
    // if (touchpad) os.touchpad = true;
    // if (blackberry) os.blackberry = true, os.version = blackberry[2];
    // if (bb10) os.bb10 = true, os.version = bb10[2];
    // if (rimtabletos) os.rimtabletos = true, os.version = rimtabletos[2];
    // if (playbook) browser.playbook = true;
    // if (kindle) os.kindle = true, os.version = kindle[1];
    // if (silk) browser.silk = true, browser.version = silk[1];
    // if (!silk && os.android && ua.match(/Kindle Fire/)) browser.silk = true;
    // if (chrome) browser.chrome = true, browser.version = chrome[1];
    if (firefox) {
        browser.firefox = true;
        browser.version = firefox[1];
    }
    // if (safari && (ua.match(/Safari/) || !!os.ios)) browser.safari = true;
    // if (webview) browser.webview = true;

    if (ie) {
        browser.ie = true;
        browser.version = ie[1];
    }

    if (edge) {
        browser.edge = true;
        browser.version = edge[1];
    }

    // It is difficult to detect WeChat in Win Phone precisely, because ua can
    // not be set on win phone. So we do not consider Win Phone.
    if (weChat) {
        browser.weChat = true;
    }

    // os.tablet = !!(ipad || playbook || (android && !ua.match(/Mobile/)) ||
    //     (firefox && ua.match(/Tablet/)) || (ie && !ua.match(/Phone/) && ua.match(/Touch/)));
    // os.phone  = !!(!os.tablet && !os.ipod && (android || iphone || webos ||
    //     (chrome && ua.match(/Android/)) || (chrome && ua.match(/CriOS\/([\d.]+)/)) ||
    //     (firefox && ua.match(/Mobile/)) || (ie && ua.match(/Touch/))));

    return {
        browser: browser,
        os: os,
        node: false,
        // 原生canvas支持，改极端点了
        // canvasSupported : !(browser.ie && parseFloat(browser.version) < 9)
        canvasSupported: !!document.createElement('canvas').getContext,
        svgSupported: typeof SVGRect !== 'undefined',
        // works on most browsers
        // IE10/11 does not support touch event, and MS Edge supports them but not by
        // default, so we dont check navigator.maxTouchPoints for them here.
        touchEventsSupported: 'ontouchstart' in window && !browser.ie && !browser.edge,
        // <http://caniuse.com/#search=pointer%20event>.
        pointerEventsSupported: 'onpointerdown' in window
            // Firefox supports pointer but not by default, only MS browsers are reliable on pointer
            // events currently. So we dont use that on other browsers unless tested sufficiently.
            // Although IE 10 supports pointer event, it use old style and is different from the
            // standard. So we exclude that. (IE 10 is hardly used on touch device)
            && (browser.edge || (browser.ie && browser.version >= 11)),
        // passiveSupported: detectPassiveSupport()
        domSupported: typeof document !== 'undefined'
    };
}