Chapter 3: Samples

Chapter03/stream-pipelines/promise-pipeline.js

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+const fs = require("fs");
+const stream = require("stream");
+const util = require("util");
+
+const pipeline = util.promisify(stream.pipeline);
+
+const uppercase = new stream.Transform({
+  transform(chunk, encoding, callback) {
+    // Data processing
+    callback(null, chunk.toString().toUpperCase());
+  },
+});
+
+async function run() {
+  await pipeline(
+    fs.createReadStream("./file.txt"),
+    uppercase,
+    fs.createWriteStream("./newFile.txt")
+  );
+  console.log("Pipeline succeeded.");
+}
+
+run().catch((err) => {
+  console.error("Pipeline failed.", err);
+});