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Managing Files and Directories



Learning how to read and write to files, and move and copy files and directories, is a basic data management skill:

  1. To open a file, use the openStream() method of the File interface.

    The method returns a FileStream object, which is a handle to the opened file.

    var documentsDir;
    
    var testFile = documentsDir.createFile("test.txt");
       if (testFile != null) 
       {
          testFile.openStream("w", onOpenSuccess, onOpenError, "UTF-8");
       }
  2. Perform all actual operations, such as reading, writing, or closing, on the file through the FileStream object based on a position attribute, which represents the current position in the file:

    function onOpenSuccess(fs)
    {
       /* Write HelloWorld to the file */
       fs.write("HelloWorld");
    
       /* Read the file content */
       fs.read(testFile.fileSize);
    
       /* Close the file */
       fs.close();
    }
    
  3. To copy a file or directory, use the copyTo() method. The following example copies the files to the images/backup/ directory. Since the third parameter is set to true, any existing files with the same name in the target directory are overwritten.

    for (var i = 0; i < files.length; i++) 
    {
       documentsDir.copyTo(files[i].fullPath, "images/backup/"+files[i].name,
                           true, onsuccess, onerror);
    }
    
  4. To move a file or directory, use the moveTo() method. The following example moves the files to the images/newFolder/ directory. Since the third parameter is set to false, no existing files with the same name in the target directory are overwritten.

    for (var i = 0; i < files.length; i++) 
    {
       documentsDir.moveTo(files[i].fullPath, "images/newFolder/"+files[i].name,
                           false, onsuccess, onerror);
    }