How to pipe to function in node.js?

Question

I want to read from file to stream, pipe the output to a function that will upperCase the content and then write to file. This is my attempt. What am I doing wrong?

Answer 1

Using async iteration is the cleaner new way to transform streams:

const fs = require('fs');
(async () => {
    const out = fs.createWriteStream('output.txt');
    for await (const chunk of fs.createReadStream('input.txt', 'utf8')) {
        out.write(chunk.toUpperCase());
    }
})();

As you can see, this way is a lot more terse and readable if you already are working in an async function context.