Why does the watch method in node.js fire more than once?

Question

Node.js

There is an index.js file:

const fs = require("fs");

var mainFile = './src/vuefy/main.js';

fs.watch(mainFile, (eventType, filename) => {
  console.log(filename);
  //build();
});

I run node index.js and when main.js changes, the watch method fires twice. Why can this happen?
I'm running under windows 8.1, node v5.12.0.

Answer 1

This is a windows API issue https://github.com/nodejs/node/issues/3042
You can use fs.watchFile instead of fs.watch, but it is very slow and as it is written in the off-doc: "Note: fs.watch() is more efficient than fs.watchFile and fs.unwatchFile. fs.watch should be used instead of fs.watchFile and fs.unwatchFile when possible."

Answer 2

Because life is pain.
Why do you think the method should be called once and make a full log output, including the event type.