downloading file with binary data. Not receiving entire contents of file.

Question

javascript, running in the browser.

using XMLHttpRequest and the content.dropboxapi.com/2/files/download endpoint to download a zip file from my dropbox folder.  I am receiving the file. But the last 100 or so bytes are missing.  Why am I not receiving the entire contents of the file?

I get the size of the file from the list_folder API. That number is a little bit larger than the length of the xhr.response property.  And when I pass xhr.response to a function that treats the response data as a zip file stream, the error says the file cannot be unzipped.  The error says missing xxx number of bytes. That number matches the number of bytes that are missing from the download.

thanks,

// ---------------------- dropbox_GetFile_http ------------------------           
function dropbox_GetFile_http( path, token )                                      
{                                                                                 
  var xhr = new XMLHttpRequest( ) ;                                              
  xhr.onreadystatechange = function( )                                           
  {                                                                               
    if ( xhr.readyState == XMLHttpRequest.DONE)                                  
    {                                                                             
      if (xhr.status == 200)                                                     
      {                                                                           
        var lx   = xhr.response.length ;                                         
        console.log( 'got data. ' + 'lgth:' + lx ) ;                              
        unzip( xhr.response ) ;                                                  
      } else                                                                      
      {                                                                           
        var msg = 'status:' + xhr.status ;                                       
        console.log( msg ) ;                                                      
      }                                                                           
    }                                                                             
  } ;

var runAsync = true ; 
  xhr.open('POST', 'https://content.dropboxapi.com/2/files/download', runAsync);
  xhr.setRequestHeader('Authorization', 'Bearer ' + token );                    
  xhr.setRequestHeader('Dropbox-API-Arg', JSON.stringify({ path: path })) ;     
  xhr.send();
}

steve_lae0901 · Accepted Answer

I was not setting the responseType of the xhr object to 'arraybuffer'.  Once I did that the download worked.

// ---------------------- dropbox_GetFile_http ------------------------           
function dropbox_GetFile_http( path, token )                                      
{                                                                                 
  var xhr = new XMLHttpRequest( ) ;                                              
  xhr.onreadystatechange = function( )                                           
  {                                                                               
    if ( xhr.readyState == XMLHttpRequest.DONE)                                  
    {                                                                             
      if (xhr.status == 200)                                                     
      {                                                                           
        var lx   = xhr.response.byteLength ;                                         
        console.log( 'got data. ' + 'lgth:' + lx ) ;                              
        unzip( xhr.response ) ;                                                  
      } else                                                                      
      {                                                                           
        var msg = 'status:' + xhr.status ;                                       
        console.log( msg ) ;                                                      
      }                                                                           
    }                                                                             
  } ;

var runAsync = true ; 
  xhr.open('POST', 'https://content.dropboxapi.com/2/files/download', runAsync);
xhr.responseType = 'arraybuffer' ;
  xhr.setRequestHeader('Authorization', 'Bearer ' + token );                    
  xhr.setRequestHeader('Dropbox-API-Arg', JSON.stringify({ path: path })) ;     
  xhr.send();
}