Getting Unprompted Input in NodeJS

Question

I'm trying to get unprompted input from the user in a NodeJS server. The reason is that I want to be able to send strings that can be interpreted as commands while a server is running such as commands to flush the cache.

Now, originally, I used readline as follows:

import * as ReadLine from 'readline';

export default function InitTerminal() {
    const terminal = ReadLine.createInterface({
        input: process.stdin,
        terminal: false
    });

    terminal.on('line', (input) => {
        console.log(input);
        switch(input.toString()) {
            default:
                console.log('Unknown Command');
                break;
        }
    });
}

The issue was that after most inputs, I would get:

rl.on line * input *

Where * input * refers to the string representation of the buffer input from process.stdin. The weird thing is, the on line triggers only occassionaly and typically I will get that line and my listener doesn't trigger. The same thing happens when I don't use ReadLine and just add a listener to process.stdin. Something is triggering node to print out the output above. I'm using node 11.12.0 and ts-node-dev for typescript in development mode.

So what I'm asking is how can I use node to get unprompted input as commands? Either by modifying my original code or any way I haven't thought of.

Kind thanks.

Sammi3 · Accepted Answer · 2019-12-15 02:37:50Z

1

The problem was that ts-node-dev plays with the stdin. That means it's hard to get the stdin while using it. What I hade to do was create an npm script called build:dev which compiled my typescript and then ran it. Then I could use the process.stdin without concern.

A way to possible watch changes while doing this is to use nodemon instead of ts-node-dev and just compile the typescript when needed

answered Dec 15, 2019 at 2:37

Sammi3

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