Node http res.end

Question

I am currently reading through "Node.js in action" as well as following through a number of online learning resources. One of the first examples in the book is showing how to pipe a stream through to a response. Like so:

var http = require('http'),
    fs = require('fs');

http.createServer(function(req, res){
    res.writeHead(200, {"Content-Type": "image/png"});
    fs.createReadStream("./image.png").pipe(res);
}).listen(xxxx)

My question is how valid is this code? I was under the impression that when ever using the http you should always end with:

res.end();

Is this not necessary as piping it implies an end? When ever writing a response should I always end it?

Answer 1

When your readable stream finishes reading (the image.png file), by default, it emits and end() event, which will call the end() event on the writable stream (the res stream). You don't need to worry about calling end() in this case.

It's worth point out that, in this scenario, your res will no longer be writable after the end() event is called. So, if you want to keep it writable, just pass the end: false option to pipe(), like:

fs.createReadStream("./image.png").pipe(res, { end: false });

, and then call the end() event sometime in the future.