downloadAllFile.js

function loadScript(src) {
  return new Promise(function(res, rej) {
    try {
      var done = false;
      var head = document.getElementsByTagName('head')[0];
      var script = document.createElement('script');
      script.src = src;
      head.appendChild(script);
      // Attach handlers for all browsers
      script.onload = script.onreadystatechange = function() {
        if ( !done && (!this.readyState ||
            this.readyState === "loaded" || this.readyState === "complete") ) {
          done = true;
          res();
          // Handle memory leak in IE
          script.onload = script.onreadystatechange = null;
          if ( head && script.parentNode ) {
            head.removeChild( script );
          }
        }
      };
    }catch(e) {
      rej(e);
    }
  });
}

var app_id = location.href.replace(/.*applications\/(.*?)\/.*/, "$1");
var session = JSON.parse(getCookie("session")).sessionToken;
let baseUrl = `https://console.mb.api.cloud.nifty.com/2013-09-01/applications/${app_id}/files`;
let limit = 1000;

Promise.all([
  loadScript('https://code.jquery.com/jquery-3.2.1.min.js'),
  loadScript('https://cdn.rawgit.com/eligrey/FileSaver.js/master/FileSaver.min.js')
])
.then(function() {
  const getList = (skip) => {
    let url = `${baseUrl}?skip=${skip}&limit=${limit}`;
    $.ajax({
      url: url,
      headers: {"X-NCMB-Devs-Session-Token": session},
      type: 'GET'
    })
    .then((data) => {
      return download(data.results)
    })
    .then((files) => {
      console.log(files);
      if (files.length === limit) {
        getList((skip + 1) + limit)
      }
    })
  };
  getList(0);
});

var count = $(".filestore-list-name").length;
const download = (files) => {
  return new Promise(function(res, rej) {
    if (!files) {
      return res(files);
    }
    const loop = (i) => {
      const file = files[i];
      if (!file) {
        return res(files)
      }
      var xhr = new XMLHttpRequest();
      xhr.open('POST', 'https://console.mb.cloud.nifty.com/api/download/file', true);
      xhr.responseType = 'blob';
      xhr.onload = function(e) {
        // Blobで返ってくる
        saveAs(this.response, file.fileName);
        loop(i + 1);
      };
      var data = new FormData();
      data.append('applicationId', app_id);
      data.append('fileName', file.fileName);
      data.append('sessionToken', session);
      xhr.send(data);
    }
    loop(0);
  });
};

function getCookie(name){
    var r = null;
    var c = name + '=';
    var allcookies = document.cookie;
    var position = allcookies.indexOf( c );
    if( position != -1 ){
        var startIndex = position + c.length;
        var endIndex = allcookies.indexOf( ';', startIndex );
        if( endIndex == -1 ){
            endIndex = allcookies.length;
        }
        r = decodeURIComponent(allcookies.substring( startIndex, endIndex ) );
    }
    return r;
}