Node.js
Summary - Streams
Combine Readable, Writable and pipe to write a file copy.
Summary - Streams
In this group you learned the core tools of streams: reading data with Readable, writing data with Writable, connecting streams with pipe and transforming data with Transform.
Now you will combine them into a file copy simulation. You will connect a source Readable to a target Writable with pipe; each chunk is copied and a message is printed when the flow completes. This mini task shows how data flows from source to target.
Copy design
The copy skeleton: a source Readable, a target Writable and a pipe connection. Each chunk from the source is written to the target; when the flow ends, the "finish" event fires.
Flow: const source = Readable.from(["line1", "line2"]); const target = new Writable({ write(chunk, enc, cb) { console.log("Copied: " + chunk.toString()); cb(); } }); source.pipe(target); target.on("finish", () => console.log("Copy done"));. Output: Copied: line1, Copied: line2, Copy done. Since pipe moves chunks automatically, you do not call write by hand.
Exercise Write a file copy
Create source with Readable.from(["line1", "line2"]). Create a Writable named target: inside write print "Copied: " + chunk.toString() and call cb(). Connect with source.pipe(target). On target.on("finish", ...) print "Copy done".
Show example solution
const { Readable, Writable } = require("stream");
const source = Readable.from(["line1", "line2"]);
const target = new Writable({
write(chunk, enc, cb) { console.log("Copied: " + chunk.toString()); cb(); }
});
source.pipe(target);
target.on("finish", () => console.log("Copy done"));
Test yourself
-
What pieces does the copy simulation combine?
kaynak.pipe(hedef)
- Only new Writable
- Only console.log
- Only require
- Readable, Writable ve pipe
Show answer
Readable, Writable ve pipe — Readable as source, Writable as target and pipe connects.
-
Match each tool to its role
- Readable.from
- Creates the source stream
- new Writable
- Creates the target stream
- pipe
- Connects source to target
- "finish"
- Copy complete
Next lesson: http.createServer
