Tizen Developers

var documentsDir;
function onsuccess(files) {
  for(var i = 0; i < files.length; i++) {
    console.log("File Name is " + files[i].name); 
  }

  var testFile = documentsDir.createFile("test.txt");

  if (testFile != null) {
    testFile.openStream(
      "w",
      function(fs){
        fs.write("HelloWorld");
        fs.close();
      }, function(e){
        console.log("Error " + e.message);
      }, "UTF-8"
    );
  }
}

function onerror(error) {
  console.log("The error " + error.message + " occurred when listing the files in the selected folder");
}

tizen.filesystem.resolve(
  '/opt/apps/you app Id/data', 
  function(dir){
    documentsDir = dir;
    dir.listFiles(onsuccess, onerror);
  }, function(e){
    console.log("Error" + e.message);
  }, "rw"
);