creating an order with IDEX API

order.js

const { soliditySha3 } = require('web3-utils');
const {
  hashPersonalMessage,
  bufferToHex,
  toBuffer,
  ecsign
} = require('ethereumjs-util')
const { mapValues } = require('lodash');

const contractAddress = '0x2a0c0dbecc7e4d658f48e01e3fa353f44050c208';
const tokenBuy = '0x0000000000000000000000000000000000000000';
const amountBuy = '100000000';
const tokenSell = '0x1111111111111111111111111111111111111111';
const amountSell = '10000';
const address = '0x034767f3c519f361c5ecf46ebfc08981c629d381';
const nonce = 5;
const expires = '10000';

const raw = soliditySha3({
  t: 'address',
  v: contractAddress
}, {
  t: 'address',
  v: tokenBuy
}, {
  t: 'uint256',
  v: amountBuy
}, {
  t: 'address',
  v: tokenSell
}, {
  t: 'uint256',
  v: amountSell
}, {
  t: 'uint256',
  v: expires
}, {
  t: 'uint256',
  v: nonce
}, {
  t: 'address',
  v: address
});
const salted = hashPersonalMessage(toBuffer(raw))
const {
  v,
  r,
  s
} = mapValues(ecsign(salted, privateKeyBuffer), (value, key) => key === 'v' ? value : bufferToHex(value));

const request = require('request');
request({
  method: 'POST',
  url: 'https://api.idex.market/order',
  json: {
    tokenBuy: tokenBuy,
    amountBuy: amountBuy,
    tokenSell: tokenSell,
    amountSell: amountSell,
    address: address,
    nonce: 5,
    expires: expires,
    v: v,
    r: r,
    s: s
  }
}, function (err, resp, body) {
  console.log(body);
})