【cordova-plugin-file】内部ストレージを使ってみた【Vue】

export default {
  methods: {
    async init() {
      // データ保存
      await this.set_data_to_internal_storage('file_name.txt', 'test data')
      // データ取得
      const data = await this.get_data_from_internal_storage('file_name.txt')
      console.log('data: ' + data)
    },
    async set_data_to_internal_storage(file_name, data) {
      console.log('start set_data_to_internal_storage')
      const fileSystem = await new Promise(function(resolve, reject) {
        window.resolveLocalFileSystemURL(
          // eslint-disable-next-line
          cordova.file.dataDirectory,
          resolve,
          reject
        )
      })
      const fileEntry = await new Promise(function(resolve, reject) {
        fileSystem.getFile(
          file_name,
          { exclusive: false, create: true },
          resolve,
          reject
        )
      })
      return new Promise((resolve, reject) => {
        fileEntry.createWriter(function(writer) {
          console.log('書き込み開始')
          // 書き込み終了時の処理を定義する
          writer.onwriteend = function(event) {
            if (this.error) {
              console.log(
                'ファイル追記 追記処理中にエラー発生',
                this.error,
                event
              )
              // Promiseの結果を返す
              reject('reject!!')
            } else {
              console.log('ファイル追記 成功', event)
              // Promiseの結果を返す
              resolve('resolve!!')
            }
          }
          // 書き込み
          writer.write(data)
        })
      })
    },
    async get_data_from_internal_storage(file_name) {
      console.log('start get_data_from_internal_storage')
      var options = {
        exclusive: false,
        create: false
      }
      const fileSystem = await new Promise(function(resolve, reject) {
        window.resolveLocalFileSystemURL(
          // eslint-disable-next-line
          cordova.file.dataDirectory,
          resolve,
          reject
        )
      })
      const fileEntry = await new Promise(function(resolve, reject) {
        fileSystem.getFile(file_name, options, resolve, reject)
      })
      return new Promise(resolve => {
        fileEntry.file(
          function(file) {
            var reader = new FileReader()

            reader.onloadend = function() {
              console.log('Successful file read: ' + this.result)
              console.log(fileEntry.fullPath + ': ' + this.result)
              resolve(this.result)
            }

            reader.readAsText(file)
          },
          function(error) {
            console.log('readFile エラーが発生', error.code)
          }
        )
      })
    }
  }
}