Tuesday, December 6, 2011

Node.js Options Parser

To put it simply options parsing is a way to pass arguments to functions in external files.  This doesn't sound like a big deal, but it is.  Let me explain.

Lets say you have all of your game functions in one giant js file, functions for calculating attack, def, etc.  A month down the road you realize that you want to change just about anything, you'll have to either rewrite a bunch or something far worse. Non-modularity is the hallmark of hard to maintain code or the 10lbs of 'stuff' in a 5lb bag.

Wouldn't it be much easier if we could just keep all of our functions separate?  Pass arguments to them in a generic and modular way?  Update a 20 line file instead of a 1,000+ line file?  We can do all of that with options parsers.

Taken from: http://www.catonmat.net/blog/nodejs-modules-optimist/

This time I'll introduce you to node-optimist - the lightweight options parser library. This library is also written by James Halliday (SubStack), my co-founder of Browserling and Testling.
Wonder how lightweight an options parser can be? Check this out:
var argv = require('optimist').argv;
And you're done! All options have been parsed for you and have been put in argv.
Here are various use cases. First off, it supports long arguments:
#!/usr/bin/env node
var argv = require('optimist').argv;

if (argv.rif - 5 * argv.xup > 7.138) {
    console.log('Buy more riffiwobbles');
else {
    console.log('Sell the xupptumblers');
Now you can run this script with --rif and --xup arguments like this:
$ ./xup.js --rif=55 --xup=9.52
Buy more riffiwobbles

$ ./xup.js --rif 12 --xup 8.1
Sell the xupptumblers
I know you want to buy more riffiwobbles and sell your xupptumblers.
I'm guessing it's in order of magnitudes more complicated, but looks to be necessary.

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