Yik Yak user-agent generator, adapted from https://github.com/soren121/yodel/

yikyakUA.js

var crypto = require('crypto')

function genRandom4DigitHex(num) {
  var arr = [];

  // Decrement num by one to align with zero-indexed array
  num--;
  for (var cur = 0; cur <= num; cur++) {
    // Get a chunk of the crypto buffer and force to string
    var ret = (Math.random()*0xFFFF<<0).toString(16)
    arr.push(ret);
  }

  return arr;
}

var version = "2.5.1e"

function genUA() {
  var base = [];
  base[0] = "Dalvik/1.6.0 (Linux; U; Android 4.4.4; ";
  base[1] = " Build/";
  base[2] = ")";

  var devices = [
    "Nexus 4",
    "Nexus 5",
    "HTC One_M8",
    "SM-N900V",
    "XT1080",
    "SM-G900V",
    "SCH-I545"
  ];

  // Select random device name
  var device = devices[Math.floor(Math.random() * (devices.length - 1)) + 1];
  // Generate random build ID
  var build = genRandom4DigitHex(2);
  build = (build[0] + build[1]).substring(0, 6).toUpperCase();

  var useragent = base[0] + device + base[1] + build + base[2];

  // Append API version
  useragent += " " + version;
  return useragent
}

console.log(genUA())