docs: improve audio example to show how to stream to a file (#598)

examples/audio.ts

@@ -1,7 +1,8 @@
 #!/usr/bin/env -S npm run tsn -T
+import 'openai/shims/node';
 
 import OpenAI, { toFile } from 'openai';
-import fs from 'fs/promises';
+import fs from 'fs';
 import path from 'path';
 
 // gets API Key from environment variable OPENAI_API_KEY
@@ -10,14 +11,34 @@ const openai = new OpenAI();
 const speechFile = path.resolve(__dirname, './speech.mp3');
 
 async function main() {
+  await streamingDemoNode();
+  await blockingDemo();
+}
+main();
+
+async function streamingDemoNode() {
+  const response = await openai.audio.speech.create({
+    model: 'tts-1',
+    voice: 'alloy',
+    input: 'the quick brown chicken jumped over the lazy dogs',
+  });
+
+  const stream = response.body;
+
+  console.log(`Streaming response to ${speechFile}`);
+  await streamToFile(stream, speechFile);
+  console.log('Finished streaming');
+}
+
+async function blockingDemo() {
   const mp3 = await openai.audio.speech.create({
     model: 'tts-1',
     voice: 'alloy',
     input: 'the quick brown fox jumped over the lazy dogs',
   });
 
   const buffer = Buffer.from(await mp3.arrayBuffer());
-  await fs.writeFile(speechFile, buffer);
+  await fs.promises.writeFile(speechFile, buffer);
 
   const transcription = await openai.audio.transcriptions.create({
     file: await toFile(buffer, 'speech.mp3'),
@@ -32,4 +53,21 @@ async function main() {
   console.log(translation.text);
 }
 
-main();
+/**
+ * Note, this is Node-specific.
+ *
+ * Other runtimes would need a different `fs`,
+ * and would also use a web ReadableStream,
+ * which is different from a Node ReadableStream.
+ */
+async function streamToFile(stream: NodeJS.ReadableStream, path: fs.PathLike) {
+  return new Promise((resolve, reject) => {
+    const writeStream = fs.createWriteStream(path).on('error', reject).on('finish', resolve);
+
+    // If you don't see a `stream.pipe` method and you're using Node you might need to add `import 'openai/shims/node'` at the top of your entrypoint file.
+    stream.pipe(writeStream).on('error', (error) => {
+      writeStream.close();
+      reject(error);
+    });
+  });
+}