The
fsPromises.appendFile() method is used to asynchronously append the given data to a file. A new file is created if it does not exist. The options parameter can be used to modify the behavior of the operation.
Syntax:
fsPromises.appendFile( path, data, options )
Parameters: This method accepts three parameters as mentioned above and described below:
- path: It is a String, Buffer, URL or number that denotes the source filename or file descriptor that will be appended to.
- data: It is a String or Buffer that denotes the data that has to be appended.
- options: It is an string or an object that can be used to specify optional parameters that will affect the output. It has three optional parameters:
- encoding: It is a string that specifies the encoding of the file. The default value is ‘utf8’.
- mode: It is an integer which specifies the file mode. The default value is ‘0fso666’.
- flag: It is a string which specifies the flag used while appending to the file. The default value is ‘a’.
Return Value: It returns the Promise.
Example: This example uses a sample txt file named "example_file" with
Hello text.
Filename: index.js
Note: Run
index.js file with below command:
node index.js
Output:
File Contents of file before append: Hello
File Contents of file after append: HelloGeeksforGeeks
Note: If options is a string, then it specifies the encoding. The path may be specified as a
FileHandle that has been opened for appending (using
fsPromises.open()).
