Google speech-to-text API示例代码不会运行

Question

我一直在不断地重读说明(设置项目，使用我的服务帐户密钥将环境变量设置为JSON文件的文件路径，安装/初始化gcloud等)。但是我根本不能运行示例代码，我也不知道为什么。示例代码如下：

// Imports the Google Cloud client library
const speech = require('@google-cloud/speech');

// Creates a client
const client = new speech.SpeechClient();

/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
const gcsUri = '.resources/audio.raw';
const encoding = 'LINEAR16';
const sampleRateHertz = 16000;
const languageCode = 'en-US';

const config = {
  encoding: encoding,
  sampleRateHertz: sampleRateHertz,
  languageCode: languageCode,
};

const audio = {
  uri: gcsUri,
};

const request = {
  config: config,
  audio: audio,
};

// Detects speech in the audio file. This creates a recognition job that you
// can wait for now, or get its result later.
const [operation] = await client.longRunningRecognize(request);
// Get a Promise representation of the final result of the job
const [response] = await operation.promise();
const transcription = response.results
  .map(result => result.alternatives[0].transcript)
  .join('\n');
console.log(`Transcription: ${transcription}`);

终端显示以下错误：

const [operation] = await client.longRunningRecognize(request);
                      ^^^^^^

SyntaxError: Unexpected identifier
    at createScript (vm.js:56:10)
    at Object.runInThisContext (vm.js:97:10)
    at Module._compile (module.js:542:28)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.runMain (module.js:604:10)
    at run (bootstrap_node.js:389:7)
    at startup (bootstrap_node.js:149:9)

我不明白为什么它是一个意外的标识符。不是创建了const客户端吗？

Answer 1

await用于异步函数，让我们将您的代码放入一个异步函数中

// Imports the Google Cloud client library
const speech = require('@google-cloud/speech');

// Creates a client
const client = new speech.SpeechClient();

/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
const gcsUri = '.resources/audio.raw';
const encoding = 'LINEAR16';
const sampleRateHertz = 16000;
const languageCode = 'en-US';

const config = {
  encoding: encoding,
  sampleRateHertz: sampleRateHertz,
  languageCode: languageCode,
};

const audio = {
  uri: gcsUri,
};

const request = {
  config: config,
  audio: audio,
};
async function main () {
// Detects speech in the audio file. This creates a recognition job that you
// can wait for now, or get its result later.
const [operation] = await client.longRunningRecognize(request);
// Get a Promise representation of the final result of the job
const [response] = await operation.promise();
const transcription = response.results
  .map(result => result.alternatives[0].transcript)
  .join('\n');
console.log(`Transcription: ${transcription}`);
}
main();

Answer 2

await关键字只能在异步函数中使用。

您可以将部分代码包装在promise函数中，然后调用该promise：

const detectSpeach = async () => {
  // Detects speech in the audio file. This creates a recognition job that you
  // can wait for now, or get its result later.
  const [operation] = await client.longRunningRecognize(request);
  // Get a Promise representation of the final result of the job
  const [response] = await operation.promise();
  const transcription = response.results
    .map(result => result.alternatives[0].transcript)
    .join('\n');
  console.log(`Transcription: ${transcription}`);
};

detectSpeach();

更多信息：https://javascript.info/async-await

Answer 3

const [operation] = await client.longRunningRecognize(request);
                  ^^^^^^
SyntaxError: Unexpected identifier

我不明白为什么它是一个意外的标识符。不是创建了const client吗？

答案是，是的，const client是初始化的，但在普通的JavaScript脚本中，await不被视为关键字。在async函数(或生成器函数)之外，await通常是一个有效的标识符，因此await后跟client的序列不是一个有效的表达式，因为client是一个意外的标识符。

要将await用作运算符，必须在async函数或生成器中进行编码。在新代码中使用await作为标识符可能是不明智的。

背景：

• ES5.1没有将await作为保留字或未来保留字，除非the goal [symbol] of the syntactic grammar is

，否则

• ES6 (ECMAScript 2015)在ECMAScript ES5.1的上下文中引入了await作为未来保留字，但提供了await作为保留字

我对这种拼凑混乱的理解是，await和async都是通过修改JavaScript解析器来检测语法错误(async function、await identifier、for await ... of)并在某些(但不是所有)上下文中进一步处理它们来检测的。