//after device is ready
var fail = function (message) {    
   alert(message)
}
var success = function (data) {
       console.log("succes");
}
cordova.plugins.DownloadManager.download("Your URL to download", "Your file name","Your Description" ,success, fail);

var options = {
  setDestinationInExternalPublicDir: true  // set true if you want to use public dir instead of files dir
}
cordova.plugins.DownloadManager.download("Your URL to download", "Your file name","Your Description" ,success, fail, options)

// Full absolute path the the already downloaded file.  It should be in file:///storage/emulated/0/Download/ or subfolder.
const filepath_sanitized = filepath.replace("file://", "");  // Note: Don't include any file:// prefix in the path.

/**
 * Method that calls the addCompletedDownload method on the DownloadManager object
 * @param {string} title Must match the filename which was written.
 * @param {string} description doesn't seem used?
 * @param {string} mimeType i.e. "text/plain"
 * @param {string} path Absolute file path. Note: Don't include any file:// prefix in the path.
 * @param {number} length size of the downloaded file
 * @param {function(string)} success callback
 * @param {function(string)} error callback
 */
cordova.plugins.DownloadManager.addCompletedDownload(filename, "Your Description", 'text/*', filepath_sanitized, length,
  (result) => {
    console.info(result);
  },
  (err) => {
    console.error(err);
  })