使用superagent 爬网站的时候使用async 对并发个数进行控制，并发个数确保了，但是数据的结果重复了：爬取的数组长度是10，最后结果输出了10次，求教该如何控制输出结果不重复(或者说如何判断全部url爬完)？ 代码如下：

var eventproxy = require('eventproxy');
var superagent = require('superagent');
var cheerio = require('cheerio');
var url = require('url');
var async = require('async');
var fs = require('fs');

var itjuziUrl = 'http://www.itjuzi.com/company/';
var companyUrls = [];
for (i = 1; i <= 10; i++) {
  var href = url.resolve(itjuziUrl, i.toString());  //
  companyUrls.push(href);
}

var companyJson = [];
var concurrencyCount = 0;
var fetchUrl= function(url ,callback){
  companyurl = url;
  concurrencyCount ++ ;
  superagent.get(companyurl)
    .end(function (err, res) {
      if(err){
          callback(err, 'fetch url:' + companyurl + ' err: ');
        return console.log('fetch url:' + companyurl + ' err: ', err);
      }
      console.log('现在并发数目是******： ',concurrencyCount,' **** fetch ' + companyurl + ' successful');
      //ep.emit('topic_html', [companyurl, res.text]);
      var $ = cheerio.load(res.text);
      concurrencyCount --;
      companyJson.push({
        productName: $('div>span.title').text().replace(/[\n\t\r\s]/g,""),
        companyName:  $('div.des-more>div> span').eq(0).text().replace(/[\n\t\r\s]/g,""),
        address: $('span.loca.c-gray-aset').text().replace(/[\n\t\r\s]/g,""),
        stage: $('td.mobile-none').text().replace(/[\n\t\r\s]/g,""),
        mainpage: $('a.weblink').attr('href'),
        hirepage: ''
      });
       callback(null, companyJson);
    });
}

async.mapLimit(companyUrls , 5, function(url,callback){
  fetchUrl(url ,callback)
},function(err, result ){
  //console.log('now  err , result  is ',result);
  if (!err) {
    console.log('result.length  ',result.length );
    if (companyUrls.length = result.length) {
      arr = result;
      var file = fs.createWriteStream('result.json');
      file.on('error', function (err) {
        console.log('write  file  error ', err);
      });
      arr.forEach(function (v) {
        //console.log('v is  ', JSON.stringify(v));
        file.write(JSON.stringify(v) + '\n');
      });
      file.end();
    }
  }
})
\n```