How to use the react-native-fs.copyFile function in react-native-fs

.then(() => {
        // Copy the database to the backup location
        console.log(
          "[Dropbox backup] DB backup file is now gone; continue with backup."
        );
        return RNFS.copyFile(this.getLocalDBFilePath(), databaseBackupFilePath);
      })
      .then(() => {

reg.logger().info('Original dimensions ', dimensions);
		if (dimensions.width > maxSize || dimensions.height > maxSize) {
			dimensions.width = maxSize;
			dimensions.height = maxSize;
		}
		reg.logger().info('New dimensions ', dimensions);

		const format = mimeType == 'image/png' ? 'PNG' : 'JPEG';
		reg.logger().info(`Resizing image ${localFilePath}`);
		const resizedImage = await ImageResizer.createResizedImage(localFilePath, dimensions.width, dimensions.height, format, 85); // , 0, targetPath);

		const resizedImagePath = resizedImage.uri;
		reg.logger().info('Resized image ', resizedImagePath);
		reg.logger().info(`Moving ${resizedImagePath} => ${targetPath}`);

		await RNFS.copyFile(resizedImagePath, targetPath);

		try {
			await RNFS.unlink(resizedImagePath);
		} catch (error) {
			reg.logger().warn('Error when unlinking cached file: ', error);
		}
	}

async copy(source, dest) {
		let retry = false;
		try {
			await RNFS.copyFile(source, dest);
		} catch (error) {
			// On iOS it will throw an error if the file already exist
			retry = true;
			await this.unlink(dest);
		}

		if (retry) await RNFS.copyFile(source, dest);
	}

Zip.unzip(JS_BUNDLE_ZIP_PATH, DOCUMENT_FILE_PATH, async (res) => {
        await deleteDir(JS_BUNDLE_ZIP_PATH);
        if (res) {
            onError && onError(ERROR_UNZIP_JS);
        } else {
            try {
                let needCopyFiles = JSON.parse(await fs.readFile(CACHE_PATH + '/needCopyFiles.json'));
                if (JS_VERISON_CODE === 0) {
                    for (let file of needCopyFiles) {
                        await fs.mkdir(CACHE_PATH + '/' + file.replace(/[^/]*$/, ''));
                        if (IS_ANDROID) {
                            await fs.copyFileRes(file.replace(/.*\/(.*)/, '$1'), CACHE_PATH + '/' + file);
                        } else {
                            await fs.copyFile(fs.MainBundlePath + '/' + file, CACHE_PATH + '/' + file);
                        }
                    }
                } else {
                    for (let file of needCopyFiles) {
                        await fs.mkdir(CACHE_PATH + '/' + file.replace(/[^/]*$/, ''));
                        await fs.copyFile(WWW_PATH + '/' + file, CACHE_PATH + '/' + file);
                    }
                }
            } catch (e) {
                console.log('unzip erorr:', e);
                await deleteDir(CACHE_PATH);
                onError && onError(ERROR_UNZIP_JS);
                return;
            }
            await deleteDir(WWW_PATH);
            await fs.unlink(CACHE_PATH + '/needCopyFiles.json');

componentWillMount() {
    RNFS.unlink(RNFS.DocumentDirectoryPath + "/nkjv.realm");
    RNFS.unlink(RNFS.DocumentDirectoryPath + "/nkjv.realm.lock");
    if (Platform.OS == "android") {
      RNFS.copyFileAssets("nkjv.realm", RNFS.DocumentDirectoryPath + "/nkjv.realm");
      RNFS.copyFileAssets("nkjv.realm.lock", RNFS.DocumentDirectoryPath + "/nkjv.realm.lock");
    } else {
      try {
        RNFS.copyFile(RNFS.MainBundlePath + "/nkjv.realm", RNFS.DocumentDirectoryPath + "/nkjv.realm");
        RNFS.copyFile(RNFS.MainBundlePath + "/nkjv.realm.lock", RNFS.DocumentDirectoryPath + "/nkjv.realm.lock");
      } catch (e) {
        console.log("FILE ALREADY EXISTS");
      }
    }
  }
  _onShowSearch() {

() => {
        if (Platform.OS == "android") {
          RNFS.copyFileAssets(`${book}.realm.lock`, RNFS.DocumentDirectoryPath + `/${book}.realm.lock`);
          RNFS.copyFileAssets(`${book}.realm`, RNFS.DocumentDirectoryPath + `/${book}.realm`).then(() => {
            this.loadPassage();
            this._bottomSheet.close();
          });
        } else {
          try {
            RNFS.copyFile(
              RNFS.MainBundlePath + `/${book}.realm.lock`,
              RNFS.DocumentDirectoryPath + `/${book}.realm.lock`
            );
            RNFS.copyFile(
              RNFS.MainBundlePath + `/${book}.realm`,
              RNFS.DocumentDirectoryPath + `/${book}.realm`
            ).then(() => {
              this.loadPassage();
              this._bottomSheet.close();
            });
          } catch (e) {
            console.log("FILE ALREADY EXISTS");
          }
        }
      }
    );

const expoDirectoryExists = await RNFS.exists(RNFS.DocumentDirectoryPath + '/ExponentExperienceData');

    if (!expoDirectoryExists) {
      console.log('Expo data was previously migrated. Exiting migration...');
      await this.migrateDataToSecureKeystore();
      return;
    }
    try {
      await RNFS.unlink(RNFS.DocumentDirectoryPath + '/RCTAsyncLocalStorage_V1');
      console.log('/RCTAsyncLocalStorage_V1 has been deleted. Continuing...');
    } catch (error) {
      console.log(error);
      console.log('/RCTAsyncLocalStorage_V1 does not exist. Continuing...');
    }
    try {
      await RNFS.copyFile(WalletMigrate.expoDataDirectory, RNFS.DocumentDirectoryPath + '/RCTAsyncLocalStorage_V1');
    } catch (error) {
      console.log('An error was encountered when trying to copy Expo data to /RCTAsyncLocalStorage_V1. Exiting migration...');
      console.log(error);
    }
    try {
      await RNFS.unlink(RNFS.DocumentDirectoryPath + '/RCTAsyncLocalStorage_V1/.DS_Store');
    } catch (error) {
      console.log('An error was encountered when trying to delete .DS_Store. Continuing migration...');
      console.log(error);
    }
    const files = await RNFS.readDir(WalletMigrate.expoDataDirectory);
    for (const file of files) {
      try {
        if (file.isFile()) {
          if (file.name === 'manifest.json') {
            const manifestFile = await RNFS.readFile(file.path);

}).then(() => {
      return copyFile(fileDetails.uri, filePath)
    }).then(() => {
      return isPasswordProtected(filePath)

loadVersion(payload, rootState) {
      const activeVersion = rootState.bible.activeVersion.value;
      if (Platform.OS == 'ios') {
        RNFS.copyFile(
          RNFS.MainBundlePath + `/${activeVersion}.realm`,
          RNFS.DocumentDirectoryPath + `/${activeVersion}.realm`,
        );
      } else {
        RNFS.copyFileAssets(`${activeVersion}.realm`, `${RNFS.DocumentDirectoryPath}/${activeVersion}.realm`);
      }
    },
    fetchVerses(payload, rootState) {

this.index++;
            const expandName = path.replace(/^.*(\..*)$/, '$1');
            await AsyncStorage.setItem(ITEM_NAME_INDEX, JSON.stringify(this.index));
            const item = {
                mediaId: this.index,
                url: DocumentPath + this.index + expandName,
                local: true,
            };
            await fs.copyFile(path, item.url);
            const taskItem = this.tempItem;
            const list = isImage ? taskItem.images : taskItem.videos;
            list.push(item);
            resolve(list);
        });
    }
    removeMediaFile (accusationId, url, isImage, noNeedChecked) {