I recently downloaded the Intel XDK IOT version and used the LED pin 13 Blink sample. I then uploaded the program onto the Edison, but it came up with a few errors; One of them being that it could not find the MRAA module. The sample code that came with it was: main.js:
var mraa = new require("mraa"); //require mraa
console.log('MRAA Version: ' + mraa.getVersion()); //write the mraa version to the Intel XDK console
var myOnboardLed = new mraa.Gpio(13); //LED hooked up to digital pin 13 (or built in pin on Galileo Gen1 & Gen2)
myOnboardLed.dir(mraa.DIR_OUT); //set the gpio direction to output
var ledState = true; //Boolean to hold the state of Led
periodicActivity(); //call the periodicActivity function
function periodicActivity()
{
  myOnboardLed.write(ledState?1:0); //if ledState is true then write a '1' (high) otherwise write a '0' (low)
  ledState = !ledState; //invert the ledState
  setTimeout(periodicActivity,1000); //call the indicated function after 1 second (1000 milliseconds)
}
package.JSON:
{
  "name": "Onboard LED Blink App",
  "description": "",
  "version": "0.0.0",
  "main": "main.js",
  "engines": {
    "node": ">=0.10.0"
  },
  "dependencies": {
  }
}