Taken from https://www.neontribe.co.uk/blog/cordova-file-plugin-examples

cordova-file-plugin-example.js

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
var errorHandler = function(fileName, e) {
  var msg = "";

  switch (e.code) {
    case FileError.QUOTA_EXCEEDED_ERR:
      msg = "Storage quota exceeded";
      break;
    case FileError.NOT_FOUND_ERR:
      msg = "File not found";
      break;
    case FileError.SECURITY_ERR:
      msg = "Security error";
      break;
    case FileError.INVALID_MODIFICATION_ERR:
      msg = "Invalid modification";
      break;
    case FileError.INVALID_STATE_ERR:
      msg = "Invalid state";
      break;
    default:
      msg = "Unknown error";
      break;
  }

  console.log("Error (" + fileName + "): " + msg);
};
var app = {
  // Application Constructor
  initialize: function() {
    document.addEventListener(
      "deviceready",
      this.onDeviceReady.bind(this),
      false
    );
  },

  // deviceready Event Handler
  //
  // Bind any cordova events here. Common events are:
  // 'pause', 'resume', etc.
  onDeviceReady: function() {
    this.receivedEvent("deviceready");
    console.log(cordova.file);
    function writeToFile(fileName, data) {
      data = JSON.stringify(data, null, "\t");
      window.resolveLocalFileSystemURL(
        cordova.file.dataDirectory,
        function(directoryEntry) {
          directoryEntry.getFile(
            fileName,
            { create: true },
            function(fileEntry) {
              fileEntry.createWriter(function(fileWriter) {
                fileWriter.onwriteend = function(e) {
                  // for real-world usage, you might consider passing a success callback
                  console.log('Write of file "' + fileName + '"" completed.');
                };

                fileWriter.onerror = function(e) {
                  // you could hook this up with our global error handler, or pass in an error callback
                  console.log("Write failed: " + e.toString());
                };

                var blob = new Blob([data], { type: "text/plain" });
                fileWriter.write(blob);
              }, errorHandler.bind(null, fileName));
            },
            errorHandler.bind(null, fileName)
          );
        },
        errorHandler.bind(null, fileName)
      );
    }

    function readFromFile(fileName, cb) {
      var pathToFile = cordova.file.dataDirectory + fileName;
      window.resolveLocalFileSystemURL(
        pathToFile,
        function(fileEntry) {
          fileEntry.file(function(file) {
            var reader = new FileReader();

            reader.onloadend = function(e) {
              cb(JSON.parse(this.result));
            };

            reader.readAsText(file);
          }, errorHandler.bind(null, fileName));
        },
        errorHandler.bind(null, fileName)
      );
    }

    writeToFile("example.json", { foo: "bar" });

    readFromFile("example.json", function(data) {
      console.log("data", JSON.stringify(data));
    });
  },

  // Update DOM on a Received Event
  receivedEvent: function(id) {
    var parentElement = document.getElementById(id);
    var listeningElement = parentElement.querySelector(".listening");
    var receivedElement = parentElement.querySelector(".received");

    listeningElement.setAttribute("style", "display:none;");
    receivedElement.setAttribute("style", "display:block;");

    console.log("Received Event: " + id);
  }
};

app.initialize();