how should i generate the array of random numbers in Node, without access to window.crypto?

gistfile1.txt

//helloblock tutorial

  var privateKey = "cND8kTK2zSJf1bTqaz5nZ2Pdqtv43kQNcwJ1Dp5XWtbRokJNS97N"
  var ecKey = new bitcoin.ECKey(privateKey)


// .ECKey() now either takes an array of randomly generated numbers or a bigDecimal as parameter

// from bitcoinjs tutorial

var randArr = new Uint8Array(32) 
window.crypto.getRandomValues(randArr)  //

var privateKeyBytes = []
for (var i = 0; i < randArr.length; ++i)
  privateKeyBytes[i] = randArr[i]

var ecKey = new bitcoin.ECKey(privateKeyBytes) //So question: how should i generate the array of random numbers in Node, without access to window.crypto?