navigator.getUserMedia || 
    (navigator.getUserMedia = navigator.mozGetUserMedia ||  navigator.webkitGetUserMedia || navigator.msGetUserMedia);

if (navigator.getUserMedia) {
    //do something
} else {
    console.log('your browser not support getUserMedia');
}

getUserMedia(streams, success, error);

navigator.getUserMedia({
    video: true,
    audio: true}, onSuccess, onError);

<video id="webcam"></video>

function onSuccess(stream) {    
var video = document.getElementById('webcam');    
//more code}

function onSuccess(stream) {    
var video = document.getElementById('webcam');    
if (window.URL) {
        video.src = window.URL.createObjectURL(stream);
    } else {
        video.src = stream;
    }

    video.autoplay = true;    //or video.play();}

function onSuccess(stream) {    
//创建一个音频环境对像
    audioContext = window.AudioContext || window.webkitAudioContext;
    context = new audioContext();    
    //将声音输入这个对像
    audioInput = context.createMediaStreamSources(stream);    
    //设置音量节点
    volume = context.createGain();
    audioInput.connect(volume);    
    //创建缓存，用来缓存声音
    var bufferSize = 2048;    
    // 创建声音的缓存节点，createJavaScriptNode方法的
    // 第二个和第三个参数指的是输入和输出都是双声道。
    recorder = context.createJavaScriptNode(bufferSize, 2, 2);    
    // 录音过程的回调函数，基本上是将左右两声道的声音
    // 分别放入缓存。
    recorder.onaudioprocess = function(e){
        console.log('recording');        
        var left = e.inputBuffer.getChannelData(0);        
        var right = e.inputBuffer.getChannelData(1);        
        // we clone the samples
        leftchannel.push(new Float32Array(left));
        rightchannel.push(new Float32Array(right));
        recordingLength += bufferSize;
    }    // 将音量节点连上缓存节点，换言之，音量节点是输入
    // 和输出的中间环节。    
    volume.connect(recorder);    
    // 将缓存节点连上输出的目的地，可以是扩音器，也可以
    // 是音频文件。    
    recorder.connect(context.destination); 

}

var dataChannelOptions = {
  ordered: false, // do not guarantee order
  maxRetransmitTime: 3000, // in milliseconds};
  var peerConnection = new RTCPeerConnection();
  // Establish your peer connection using your signaling channel herevar dataChannel =
  peerConnection.createDataChannel("myLabel", dataChannelOptions);

dataChannel.onerror = function (error) {
  console.log("Data Channel Error:", error);
};

dataChannel.onmessage = function (event) {
  console.log("Got Data Channel Message:", event.data);
};

dataChannel.onopen = function () {
  dataChannel.send("Hello World!");
};

dataChannel.onclose = function () {
  console.log("The Data Channel is Closed");
};