Node.js includes fs module to access physical file system. The fs module is responsible for all the asynchronous or synchronous file I/O operations.
Use fs.readFile() method to read the physical file asynchronously.
fs.readFile(fileName [,options], callback)
Use fs.writeFile() method to write data to a file. If file already exists then it overwrites the existing content otherwise it creates a new file and writes data into it.
fs.writeFile(filename, data[, options], callback)