text: // 验证当前浏览器是否支持webrtc
  // created by @HenrikJoreteg
  (function () {
  
      var prefix;
      var version;
  
      if (window.mozRTCPeerConnection || navigator.mozGetUserMedia) {
          prefix = 'moz';
          version = parseInt(navigator.userAgent.match(/Firefox\/([0-9]+)\./)[1], 10);
      } else if (window.webkitRTCPeerConnection || navigator.webkitGetUserMedia) {
          prefix = 'webkit';
          version = navigator.userAgent.match(/Chrom(e|ium)/) && parseInt(navigator.userAgent.match(/Chrom(e|ium)\/([0-9]+)\./)[2], 10);
      }
  
      var PC = window.RTCPeerConnection || window.mozRTCPeerConnection || window.webkitRTCPeerConnection;
      var IceCandidate = window.mozRTCIceCandidate || window.RTCIceCandidate;
      var SessionDescription = window.mozRTCSessionDescription || window.RTCSessionDescription;
      var MediaStream = window.webkitMediaStream || window.MediaStream;
      var screenSharing = window.location.protocol === 'https:' &&
          ((prefix === 'webkit' && version >= 26) ||
              (prefix === 'moz' && version >= 33))
      var AudioContext = window.AudioContext || window.webkitAudioContext;
      var AudioDestination = AudioContext && new AudioContext().createMediaStreamSource && new AudioContext().createMediaStreamDestination
      var videoEl = document.createElement('video');
      var supportVp8 = videoEl && videoEl.canPlayType && videoEl.canPlayType('video/webm; codecs="vp8", vorbis') === "probably";
      var getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.msGetUserMedia || navigator.mozGetUserMedia;
  
      // export support flags and constructors.prototype && PC
      window.rtcSupport = {
          prefix: prefix,
          browserVersion: version,
          support: !!PC && !!getUserMedia,
          // new support style
          supportRTCPeerConnection: !!PC,
          supportVp8: supportVp8,
          supportGetUserMedia: !!getUserMedia,
          supportDataChannel: !!(PC && PC.prototype && PC.prototype.createDataChannel),
          supportWebAudio: !!(AudioContext && AudioContext.prototype.createMediaStreamSource && AudioDestination),
          supportMediaStream: !!(MediaStream && MediaStream.prototype.removeTrack),
          supportScreenSharing: !!screenSharing,
          // constructors
          AudioContext: AudioContext,
          PeerConnection: PC,
          SessionDescription: SessionDescription,
          IceCandidate: IceCandidate,
          MediaStream: MediaStream,
          getUserMedia: getUserMedia
      };
  
  })()