fs.writeFile(file, data[, options], callback)

• file <string> | <Buffer> | <URL> | <integer> 文件名或文件描述符
• data <string> | <Buffer> | <TypedArray> | <DataView>
• options <Object> | <string>
  • encoding <string> | <null> 默认值: 'utf8'
  • mode <integer> 默认值: 0o666
  • flag <string> 请参阅对文件系统 flags 的支持。 默认值: 'w'。
• callback <Function>
  • err <Error>

当 file 是文件名时，将数据异步地写入文件，如果文件已存在则替换该文件。 data 可以是字符串或缓冲区。

当 file 是文件描述符时，其行为类似于直接调用 fs.write()（推荐）。 请参阅以下有关使用文件描述符的说明。

如果 data 是缓冲区，则忽略 encoding 选项。

const data = new Uint8Array(Buffer.from('Hello Node.js'));
fs.writeFile('message.txt', data, (err) => {
  if (err) throw err;
  console.log('The file has been saved!');
});

如果 options 是字符串，则它指定编码：

fs.writeFile('message.txt', 'Hello Node.js', 'utf8', callback);

在同一个文件上多次使用 fs.writeFile() 而不等待回调是不安全的。 对于这种情况，建议使用 fs.createWriteStream()。

• file <string> | <Buffer> | <URL> | <integer> filename or file descriptor
• data <string> | <Buffer> | <TypedArray> | <DataView>
• options <Object> | <string>
  • encoding <string> | <null> Default: 'utf8'
  • mode <integer> Default: 0o666
  • flag <string> See support of file system flags. Default: 'w'.
• callback <Function>
  • err <Error>

When file is a filename, asynchronously writes data to the file, replacing the file if it already exists. data can be a string or a buffer.

When file is a file descriptor, the behavior is similar to calling fs.write() directly (which is recommended). See the notes below on using a file descriptor.

The encoding option is ignored if data is a buffer.

const data = new Uint8Array(Buffer.from('Hello Node.js'));
fs.writeFile('message.txt', data, (err) => {
  if (err) throw err;
  console.log('The file has been saved!');
});

If options is a string, then it specifies the encoding:

fs.writeFile('message.txt', 'Hello Node.js', 'utf8', callback);

It is unsafe to use fs.writeFile() multiple times on the same file without waiting for the callback. For this scenario, fs.createWriteStream() is recommended.