Gets the float value of a Steam inventory item

steamGetFloatValue.js

'use strict';
/*jshint node:true */

// npm install lodash colors minimist request sync-request

var _           = require('lodash'),
    colours     = require('colors/safe'),
    parseArgs   = require('minimist'),
    request     = require('request'),
    requestSync = require('sync-request'),
    usage       = 'usage: STEAM_API_KEY=<steam api key> node steamGetFloatValue.js -u <item URL> || -s <steam id> -i <asset id>  [ -g <game id> ]';

var argv = parseArgs(process.argv.slice(2), {string: 's' }); // force -s value to string, JS can't handle a number that large

var apiKey  = process.env.STEAM_API_KEY,
    gameId  = argv.g || '730',
    itemId  = argv.i,
    steamId = argv.s,
    itemUrl = argv.u;

if (!apiKey) {
  console.log(colours.red('STEAM_API_KEY environment variable not set.'));
  console.log(usage);
  process.exit(1);
}

if (!itemUrl && (!itemId || !steamId)) {
  console.log(colours.red('missing item or steam id'));
  console.log(usage);
  process.exit(1);
}

if (itemUrl) {
  // split itemUrl on slashes
  var arrItemUrl = itemUrl.split('/');
  // if a vanity profile is present
  if (arrItemUrl[3] === 'id') {
    // convert name to steamID
    steamId = getSteamIdFromSteamName(arrItemUrl[4]);
  } else {
    steamId = arrItemUrl[4].toString();
  }
  // split 7th array item on underscore
  var arrItemId = arrItemUrl[6].split('_');
  // assetid is 3rd item in underscore split array
  itemId = arrItemId[2];
}

var url = 'http://api.steampowered.com/IEconItems_' +
          gameId + '/GetPlayerItems/v0001/?key=' +
          apiKey + '&SteamID=' + steamId;

var userAgent = 'Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36';

var options = {
  url: url,
  headers: {
    'User-Agent': userAgent
  }
};

//
// main
//

//console.log('trying url ' + url);
doApiCall(options, gameId, steamId, itemId);

//
// end main
//

function doApiCall(options, gameId, steamId, itemId) {
  request.get(options, function(err, res, body) {
  //console.log('got response: ' + res);
    if (!res || res.statusCode === 503) {
      console.log(colours.yellow('Steam API crapping out, trying again'));
      //sleep 1 sec then doApiCall();
      setTimeout(doApiCall(options, gameId, steamId, itemId), 1000);
    } else {
      // body comes back as JSON
      var inventory = JSON.parse(body);
      // if we get a good response, search inventory for item id
      if (inventory && inventory.result.status === 1) {
        // console.log('looking for item ' + itemId);
        var item = _.find(inventory.result.items, { 'id': parseInt(itemId) });

        if (item) {
          var float = _.find(item.attributes, { 'defindex': 8 });
          console.log('found item ' + colours.green(getMarketHashName(gameId, steamId, itemId)) +
                       ' / id: ' + item.id +
                       ' / original_id : ' + item.original_id +
                       ' / float value: ' + colours.green(float.float_value.toString().substr(0,7))
                     );
        } else {
          console.log(colours.red('item id ' + itemId + ' not found in user inventory'));
          process.exit();
        }
      } else {
	    //console.dir(body);
        console.log(colours.red('got an empty or bad response - check user id'));
        process.exit();
      }
    }
  });
}

function getSteamIdFromSteamName(steamName) {
  var resolveVanityUrl = 'http://api.steampowered.com/ISteamUser/ResolveVanityURL/v0001/?key=' +
                         apiKey + '&vanityurl=' + steamName;

  var res = requestSync('GET', resolveVanityUrl);

  var result = JSON.parse(res.getBody());

  if (result.response.success == 1) {
    console.log('using steamID: ' + result.response.steamid);
    return result.response.steamid.toString();
  } else {
    throw 'steamId not returned';
  }
}

function getMarketHashName(gameId, steamId, itemId) {

  var inventoryJsonUrl = 'http://steamcommunity.com/profiles/' + steamId + '/inventory/json/' + gameId + '/2/trading=1';

  var res = requestSync('GET', inventoryJsonUrl);

  var result = JSON.parse(res.getBody());

  if (result.success) {
    var classId = result.rgInventory[itemId.toString()].classid,
        instanceId = result.rgInventory[itemId.toString()].instanceid;

    return result.rgDescriptions[classId + '_' + instanceId].market_hash_name;

  } else {
    throw 'JSON inventory not returned';
  }

}

Hello. Can you please show me - where can i find this info -<item URL> || -s <steam id> -i <asset id> [ -g <game id> ]'; ?
Usage - this one what need change or no? Thnx for answer!