const promisifiedOldGUM = function(constraints) {
 // First get ahold of getUserMedia, if present
 const getUserMedia =
 navigator.getUserMedia ||
 navigator.webkitGetUserMedia ||
 navigator.mozGetUserMedia;
 
 // Some browsers just don't implement it - return a rejected promise with an error
 // to keep a consistent interface
 if (!getUserMedia) {
 return Promise.reject(
 new Error('getUserMedia is not implemented in this browser')
 );
 }
 
 // Otherwise, wrap the call to the old navigator.getUserMedia with a Promise
 return new Promise(function(resolve, reject) {
 getUserMedia.call(navigator, constraints, resolve, reject);
 });
};
 
// Older browsers might not implement mediaDevices at all, so we set an empty object first
if (navigator.mediaDevices === undefined) {
 navigator.mediaDevices = {};
}
 
// Some browsers partially implement mediaDevices. We can't just assign an object
// with getUserMedia as it would overwrite existing properties.
// Here, we will just add the getUserMedia property if it's missing.
if (navigator.mediaDevices.getUserMedia === undefined) {
 navigator.mediaDevices.getUserMedia = promisifiedOldGUM;
}

navigator.mediaDevices.getUserMedia(constraints).then(
 function(mediaStream) {
 // 成功
 },
 function(error) {
 // 失敗
 const { name } = error;
 let errorMessage;
 switch (name) {
 // 用戶(hù)拒絕
 case 'NotAllowedError':
 case 'PermissionDeniedError':
 errorMessage = '用戶(hù)已禁止網(wǎng)頁(yè)調(diào)用錄音設(shè)備';
 break;
 // 沒(méi)接入錄音設(shè)備
 case 'NotFoundError':
 case 'DevicesNotFoundError':
 errorMessage = '錄音設(shè)備未找到';
 break;
 // 其它錯(cuò)誤
 case 'NotSupportedError':
 errorMessage = '不支持錄音功能';
 break;
 default:
 errorMessage = '錄音調(diào)用錯(cuò)誤';
 window.console.log(error);
 }
 return errorMessage;
 }
);

// 一些初始化
const audioContext = new AudioContext();
const sourceNode = audioContext.createMediaStreamSource(mediaStream);
const scriptNode = audioContext.createScriptProcessor(
 BUFFER_SIZE,
 INPUT_CHANNELS_NUM,
 OUPUT_CHANNELS_NUM
);
sourceNode.connect(this.scriptNode);
scriptNode.connect(this.audioContext.destination);
// 監(jiān)聽(tīng)錄音的過(guò)程
scriptNode.onaudioprocess = event => {
 if (!this.isRecording) return; // 判斷是否正則錄音
 this.buffers.push(event.inputBuffer.getChannelData(0)); // 獲取當(dāng)前頻道的數(shù)據(jù)，并寫(xiě)入數(shù)組
};

const getDuration = () => {
    return (4096 * this.buffers.length) / this.audioContext.sampleRate // 4096為一個(gè)流的長(zhǎng)度，sampleRate 為采樣率
}

getVoiceSize = analyser => {
 const dataArray = new Uint8Array(analyser.frequencyBinCount);
 analyser.getByteFrequencyData(dataArray);
 const data = dataArray.slice(100, 1000);
 const sum = data.reduce((a, b) => a + b);
 return sum;
};