How to hide password in the nodejs console?

Question

I want to hide password input. I see many answers in stackoverflow but I can't verify value if I press backspace. The condition return false.

I tried several solution to overwrite the function but I got an issue with buffer if I press backspace, I got invisible character \b.

I press : "A", backspace, "B", I have in my buffer this : "\u0041\u0008\u0042" (toString() = 'A\bB') and not "B".

I have :

var readline = require('readline');  var rl = readline.createInterface({     input: process.stdin,     output: process.stdout });  rl.question("password : ", function(password) {     console.log("Your password : " + password); }); 

Answer 1

This can be handled with readline by intercepting the output through a muted stream, as is done in the read project on npm (https://github.com/isaacs/read/blob/master/lib/read.js):

var readline = require('readline'); var Writable = require('stream').Writable;  var mutableStdout = new Writable({   write: function(chunk, encoding, callback) {     if (!this.muted)       process.stdout.write(chunk, encoding);     callback();   } });  mutableStdout.muted = false;  var rl = readline.createInterface({   input: process.stdin,   output: mutableStdout,   terminal: true });  rl.question('Password: ', function(password) {   console.log('\nPassword is ' + password);   rl.close(); });  mutableStdout.muted = true; 

Answer 2

Overwrite _writeToOutput of application's readline interface : https://github.com/nodejs/node/blob/v9.5.0/lib/readline.js#L291

To hide your password input, you can use :

FIRST SOLUTION : "password : [=-]"

This solution has animation when you press a touch :

password : [-=] password : [=-] 

The code :

var readline = require('readline');  var rl = readline.createInterface({   input: process.stdin,   output: process.stdout });  rl.stdoutMuted = true;  rl.query = "Password : "; rl.question(rl.query, function(password) {   console.log('\nPassword is ' + password);   rl.close(); });  rl._writeToOutput = function _writeToOutput(stringToWrite) {   if (rl.stdoutMuted)     rl.output.write("\x1B[2K\x1B[200D"+rl.query+"["+((rl.line.length%2==1)?"=-":"-=")+"]");   else     rl.output.write(stringToWrite); }; 

This sequence "\x1B[2K\x1BD" uses two escapes sequences :

• Esc [2K : clear entire line.
• Esc D : move/scroll window up one line.

To learn more, read this : http://ascii-table.com/ansi-escape-sequences-vt-100.php

SECOND SOLUTION : "password : ****"

var readline = require('readline');  var rl = readline.createInterface({   input: process.stdin,   output: process.stdout });  rl.stdoutMuted = true;  rl.question('Password: ', function(password) {   console.log('\nPassword is ' + password);   rl.close(); });  rl._writeToOutput = function _writeToOutput(stringToWrite) {   if (rl.stdoutMuted)     rl.output.write("*");   else     rl.output.write(stringToWrite); }; 

You can clear history with :

rl.history = rl.history.slice(1);