module.exports is the object that's actually returned as the result of a require call.
The exports variable is initially set to that same object (i.e. it's a shorthand "alias"), so in the module code you would usually write something like this:
let myFunc1 = function() { ... };
let myFunc2 = function() { ... };
exports.myFunc1 = myFunc1;
exports.myFunc2 = myFunc2;
to export (or "expose") the internally scoped functions myFunc1 and myFunc2.
And in the calling code you would use:
const m = require('./mymodule');
m.myFunc1();
where the last line shows how the result of require is (usually) just a plain object whose properties may be accessed.
NB: if you overwrite exports then it will no longer refer to module.exports. So if you wish to assign a new object (or a function reference) to exports then you should also assign that new object to module.exports
It's worth noting that the name added to the exports object does not have to be the same as the module's internally scoped name for the value that you're adding, so you could have:
let myVeryLongInternalName = function() { ... };
exports.shortName = myVeryLongInternalName;
// add other objects, functions, as required
followed by:
const m = require('./mymodule');
m.shortName(); // invokes module.myVeryLongInternalName
See the docs for the update command:
npm update [-g] [<pkg>...]
This command will update all the packages listed to the latest version (specified by the tag config), respecting semver.
Additionally, see the documentation on Node.js and NPM installation and Upgrading NPM.
The following original answer is from the old FAQ that no longer exists, but should work for Linux and Mac:
How do I update npm?
npm install -g npm
Please note that this command will remove your current version of npm. Make sure to use sudo npm install -g npm if on a Mac.
You can also update all outdated local packages by doing npm update without any arguments, or global packages by doing npm update -g.
Occasionally, the version of npm will progress such that the current version cannot be properly installed with the version that you have installed already. (Consider, if there is ever a bug in the update command.) In those cases, you can do this:
curl https://www.npmjs.com/install.sh | sh
To update Node.js itself, I recommend you use nvm, the Node Version Manager.
Best Answer
A Duplex stream can be thought of a readable stream with a writable stream. Both are independent and each have separate internal buffer. The reads and writes events happen independently.
A Transform stream is a duplex where the read and write takes place in a causal way. The end points of the duplex stream are linked via some transform. Read requires write to have occurred.