How we can write a file in Node JS?

var fs = require("fs");

console.log("Write in existing file");
fs.writeFile('file.txt', 'This is test msg', function(err) {
   if (err) {
      return console.error(err);
   }  
   console.log("Written successfully!");
   console.log("Read latest written data");
   
   fs.readFile('file.txt', function (err, data) {
      if (err) {
         return console.error(err);
      }
      console.log("Read: " + data.toString());
   });
});