node pi-gpio won't work on raspberry pi while

I am new to raspberry and nodejs, what I am trying to achieve is take a picture from webcam after pressing physical button and sending it to the server.

I have raspberry pi set up with node.js installed , after installing pi-gpio and all modules required(plus onoff module), first I got error about missing module (gpio), so i used linked module to my project directory and after running the node js script i got this error:

/var/www/node $ node button.js 

/usr/local/lib/node_modules/rpi-gpio/rpi-gpio.js:355
    if (cb) return cb(err);
                   ^
TypeError: string is not a function
   at /usr/local/lib/node_modules/rpi-gpio/rpi-gpio.js:355:24
   at fs.js:949:21
   at Object.oncomplete (fs.js:107:15)

Any help would be greatly appreciable

code for buttn.js

var gpio = require('rpi-gpio');

gpio.on('change', function(channel, value) {
   console.log('Channel ' + channel + ' value is now ' + value);
});
 gpio.setup(23, gpio.DIR_IN);