How to capture the arrow keys in node.js

Question

What is the utf8 code for all four arrow keys (up down left right)?

I am learning node.js and I am trying to detect whenever these keys are being pressed.

Here is what I did, but none of it capturing the arrow keys... I am a complete newbie to node.js so I might be doing something hilariously stupid here.

var stdin = process.stdin; stdin.setRawMode(true); stdin.resume(); stdin.setEncoding('utf8');  stdin.on('data', function(key){     if (key === '39') {         process.stdout.write('right');      }     if (key === 39) {         process.stdout.write('right');      }     if (key == '39') {             process.stdout.write('right');      }     if (key == 39) {         process.stdout.write('right');      }      if (key == '\u0003') { process.exit(); }    // ctrl-c }); 

Thanks.

Answer 1

You can use keypress package. Trying the example given on the page.

var keypress = require('keypress');  // 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();   } });  process.stdin.setRawMode(true); process.stdin.resume(); 

You get the UTF-8 values of arrow keys at sequence.

> process.stdin.resume();got "keypress" { name: 'up',   ctrl: false,   meta: false,   shift: false,   sequence: '\u001b[A',   code: '[A' } > got "keypress" { name: 'down',   ctrl: false,   meta: false,   shift: false,   sequence: '\u001b[B',   code: '[B' } got "keypress" { name: 'right',   ctrl: false,   meta: false,   shift: false,   sequence: '\u001b[C',   code: '[C' } got "keypress" { name: 'left',   ctrl: false,   meta: false,   shift: false,   sequence: '\u001b[D',   code: '[D' } 

Answer 2

This should solve your problem:

var stdin = process.stdin; stdin.setRawMode(true); stdin.resume(); stdin.setEncoding('utf8');  stdin.on('data', function(key){     if (key == '\u001B\u005B\u0041') {         process.stdout.write('up');      }     if (key == '\u001B\u005B\u0043') {         process.stdout.write('right');      }     if (key == '\u001B\u005B\u0042') {         process.stdout.write('down');      }     if (key == '\u001B\u005B\u0044') {         process.stdout.write('left');      }      if (key == '\u0003') { process.exit(); }    // ctrl-c }); 

This could also be of interest for you:

stdin.on('data', function(key){     console.log(toUnicode(key)); //Gives you the unicode of the pressed key     if (key == '\u0003') { process.exit(); }    // ctrl-c });  function toUnicode(theString) {   var unicodeString = '';   for (var i=0; i < theString.length; i++) {     var theUnicode = theString.charCodeAt(i).toString(16).toUpperCase();     while (theUnicode.length < 4) {       theUnicode = '0' + theUnicode;     }     theUnicode = '\\u' + theUnicode;     unicodeString += theUnicode;   }   return unicodeString; } 

I found the function here: http://buildingonmud.blogspot.de/2009/06/convert-string-to-unicode-in-javascript.html