How to install npm packages from your local machine

If you need to manually test a package you are developing and don’t want to make a release each time you modify something, you can install it
directly from your local machine.

You can achieve this by using the following commands, depending on the package manager you use:

yarn add [path-to-your-package]

npm install [path-to-your-package]

This will have the following equivalent in package.json:

...
"dependencies": {
"[package]": "file:[relative-path-to-package]",
...
},

Write to file with JavaScript and Node.js

Sometimes, as a programmer, you might need to write something to a file on the local file system.
And that can be a piece of cake, case in which you’ll use your favorite text editor to do it
manually.
However, other times, it needs to be something complex and dynamic and you want your JavaScript to do it for you.

We’ll first require the fs module from Node.js into our JS file.

const fs = require("fs");

Then we’ll grab our content:

const content = "Hello World!";

And finally we’ll use the writeFile function from the fs module to populate our file.
We need to provide the name of our file, the data or content to populate it with, the options (
optional—for encoding, modes or flags) and a callback (also optional - to show the error message should one arise).

fs.writeFile(filename, data, [options], [callback]);

Here I’ve given it the a+ flag - “Open file for reading and appending. The file is created if it does not exist.”. The encoding defaults to ‘
utf8’ if none is given.

fs.writeFile("file.txt", content, {flag: "a+"}, (err) => {
    if (err) throw err;
});