nodejs how to read keystrokes from stdin - input

Question

Is it possible to listen for incoming keystrokes in a running nodejs script?
If I use process.openStdin() and listen to its 'data' event then the input is buffered until the next newline, like so:
// stdin_test.js
var stdin = process.openStdin();
stdin.on('data', function(chunk) { console.log("Got chunk: " + chunk); });
Running this, I get:
$ node stdin_test.js
<-- type '1'
<-- type '2'
<-- hit enter
Got chunk: 12
What I'd like is to see:
$ node stdin_test.js
<-- type '1' (without hitting enter yet)
Got chunk: 1
I'm looking for a nodejs equivalent to, e.g., getc in ruby
Is this possible?

Answer 1

For those finding this answer since this capability was stripped from tty, here's how to get a raw character stream from stdin:
var stdin = process.stdin;
// without this, we would only get streams once enter is pressed
stdin.setRawMode( true );
// resume stdin in the parent process (node app won't quit all by itself
// unless an error or process.exit() happens)
stdin.resume();
// i don't want binary, do you?
stdin.setEncoding( 'utf8' );
// on any data into stdin
stdin.on( 'data', function( key ){
// ctrl-c ( end of text )
if ( key === '\u0003' ) {
process.exit();
}
// write the key to stdout all normal like
process.stdout.write( key );
});
pretty simple - basically just like process.stdin's documentation but using setRawMode( true ) to get a raw stream, which is harder to identify in the documentation.

Answer 2

You can achieve it this way, if you switch to raw mode:
var stdin = process.openStdin();
require('tty').setRawMode(true);
stdin.on('keypress', function (chunk, key) {
process.stdout.write('Get Chunk: ' + chunk + '\n');
if (key && key.ctrl && key.name == 'c') process.exit();
});

Answer 3

In node >= v6.1.0:
const readline = require('readline');
readline.emitKeypressEvents(process.stdin);
if (process.stdin.setRawMode != null) {
process.stdin.setRawMode(true);
}
process.stdin.on('keypress', (str, key) => {
console.log(str)
console.log(key)
})
See https://github.com/nodejs/node/issues/6626

Answer 4

This version uses the keypress module and supports node.js version 0.10, 0.8 and 0.6 as well as iojs 2.3. Be sure to run npm install --save keypress.
var keypress = require('keypress')
, tty = require('tty');
// make `process.stdin` begin emitting "keypress" events
keypress(process.stdin);
// listen for the "keypress" event
process.stdin.on('keypress', function (ch, key) {
console.log('got "keypress"', key);
if (key && key.ctrl && key.name == 'c') {
process.stdin.pause();
}
});
if (typeof process.stdin.setRawMode == 'function') {
process.stdin.setRawMode(true);
} else {
tty.setRawMode(true);
}
process.stdin.resume();

Answer 5

With nodejs 0.6.4 tested (Test failed in version 0.8.14):
rint = require('readline').createInterface( process.stdin, {} );
rint.input.on('keypress',function( char, key) {
//console.log(key);
if( key == undefined ) {
process.stdout.write('{'+char+'}')
} else {
if( key.name == 'escape' ) {
process.exit();
}
process.stdout.write('['+key.name+']');
}
});
require('tty').setRawMode(true);
setTimeout(process.exit, 10000);
if you run it and:
<--type '1'
{1}
<--type 'a'
{1}[a]
Important code #1:
require('tty').setRawMode( true );
Important code #2:
.createInterface( process.stdin, {} );

Answer 6

This will output each keypress. Change console.log with whatever code you like.
process.stdin.setRawMode(true).setEncoding('utf8').resume().on('data',k=>console.log(k))

Answer 7

Based on Dan Heberden's answer, here's an async function -
async function getKeypress() {
return new Promise(resolve => {
var stdin = process.stdin
stdin.setRawMode(true) // so get each keypress
stdin.resume() // resume stdin in the parent process
stdin.once('data', onData) // like on but removes listener also
function onData(buffer) {
stdin.setRawMode(false)
resolve(buffer.toString())
}
})
}
Use like so -
console.log("Press a key...")
const key = await getKeypress()
console.log(key)

Answer 8

if(process.stdout.isTTY){
process.stdin.on("readable",function(){
var chunk = process.stdin.read();
if(chunk != null) {
doSomethingWithInput(chunk);
}
});
process.stdin.setRawMode(true);
} else {
console.log("You are not using a tty device...");
}