uartwrite.js

var fs =require( 'fs');
var devfn='/dev/ttyS1'
var txFd = fs.openSync( devfn, 'w');
var rxfd = fs.openSync( devfn, 'r');
var txBuf = new Buffer('hello');

var txBytesWritten = fs.writeSync(txFd, txBuf, 0, txBuf.length, -1);

console.log("written bytes=", txBytesWritten);
fs.closeSync(txFd);