Download.js

import Promise from 'promise-polyfill';
import fetchPonyfill from 'fetch-ponyfill';

if (!window.Promise) {
  window.Promise = Promise;
}
const {fetch, Request, Response, Headers} = fetchPonyfill();

export default class Download {
  constructor(url, name){
    this.url = url;
    this.name = name;
  }

  buildheader(headers){
    return window.session.applySessionHeader(headers);
  }

  buildRequest(){
    var params = {
      method: "GET",
      headers: this.buildheader({})
    };

    return new Request(this.url, params);
  }

  getExtension(){
    if(this.url.indexOf('export') != -1 || this.url.indexOf('print') != -1){
      if(this.url.indexOf('export') != -1){
        extension = '.xls'
      }else{
        extension = '.pdf'
      }
    }else{
      var extension = "." + this.url.split('.').pop();
    }

    return extension;
  }

  download(){
    fetch(this.buildRequest())
    .then(response => response.blob())
    .then((blob) => {
      if (window.navigator && window.navigator.msSaveOrOpenBlob) {
        window.navigator.msSaveOrOpenBlob(blob);
      }else{
        var url = URL.createObjectURL(blob)
        var a = document.createElement("a");
        document.body.appendChild(a);
        a.style = "display: none";
        a.href = url;
        a.download = this.name + this.getExtension();
        a.click();
        URL.revokeObjectURL(url);

      }
    })
  }
}