Copy all the documents from site to local directory

<button type="button"  onclick="do_dl();">Test downloading 3 text files.</button>


<script>
 SP.SOD.executeFunc('sp.js', 'SP.ClientContext');
var siteurl="https://****.sharepoint.com/sites/DEV/";
function GetDocuments(success,failure) {
debugger;
    $.ajax({
        url: siteurl + "/_api/web/lists/getbytitle('Documents')/items?$select=EncodedAbsUrl&$expand=File",
        method: "GET",
        headers: { "Accept": "application/json; odata=verbose" },
        success: function (data) {
           success(data.d.results);   
        },
        error: function (data) {
        debugger;
            failure(data);         
        }     
    });
}
function GetDocumentsSuccess(arrayname)
{
debugger;
alert("Success");

       download_files([
      { download: arrayname[0].EncodedAbsUrl, filename: arrayname[0].File.Name},
      { download: arrayname[1].EncodedAbsUrl, filename: arrayname[1].File.Name},
      { download: arrayname[2].EncodedAbsUrl, filename: arrayname[2].File.Name},
      { download: arrayname[3].EncodedAbsUrl, filename: arrayname[2].File.Name},
      { download: arrayname[4].EncodedAbsUrl, filename: arrayname[2].File.Name},
      { download: arrayname[5].EncodedAbsUrl, filename: arrayname[2].File.Name},
    ]);                     
}
function GetDocumentsFailure()
{
alert("Failure");
}


function download_files(files) {
debugger;
  function download_next(i) {
  debugger;
    if (i >= files.length) {
      return;
    }
    var a = document.createElement('a');
    a.href = files[i].download;
    a.target = '_parent';
    // Use a.download if available, it prevents plugins from opening.
    if ('download' in a) {
      a.download = files[i].filename;
    }
    // Add a to the doc for click to work.
    (document.body || document.documentElement).appendChild(a);
    if (a.click) {
      a.click(); // The click method is supported by most browsers.
    } else {
      $(a).click(); // Backup using jquery
    }
    // Delete the temporary link.
    a.parentNode.removeChild(a);
    // Download the next file with a small timeout. The timeout is necessary
    // for IE, which will otherwise only download the first file.
    setTimeout(function() {
      download_next(i + 1);
    }, 500);
  }
  // Initiate the first download.
  download_next(0);
}

</script>