calmh / yardstick

[UNMAINTAINED] Javascript code metrics

This project is not actively maintained

Issues and pull requests on this repository may not be acted on in a timely manner, or at all. You are of course welcome to use it anyway. You are even more welcome to fork it and maintain the results.

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yardstick

Code metrics for Javascript

How

Install it:

% sudo npm install -g yardstick

Run it on one or more code files:

% yardstick mole.js 
Scope          CC  Ar  Cd   Cm   Cm/Cd
mole.js        79  -   415  162     39
  anon@55       1   1    3    0      0
  readCert      2   0   11    3     27
  init          2   1    8    5     63
  register      2   1   17   12     71
    anon@274    1   1   10    5     50
  token         2   1    9    2     22
    anon@307    1   1    3    0      0
...

Reported Metrics

• CC: Estimated cyclomatic complexity. "Estimated", since this is a hard nut to crack on Javascript without actually running the code. The estimate is fairly good however and the point being "higher number => higer complexity => not necessarily so good" is still valid.

• Ar: Arity of the function.

• Cd: Number of lines of code, excluding blanks and comments.

• Cm: Number of lines of comments.

• Cm/Cd: Ratio of comments to code, as a percentage. So 100 means there are as many lines of comments as there are lines of code, while 25 means there are four times as many lines of code.

But metrics such as cyclomatic complexity and number of comments are useless!

By themselves, possibly. But they can be a handy guide for evaluating areas of code that could use some love. It's a tool like anything else.

The cyclomatic complexity reported by yardstick differs from $othertool!

Like I said, calculating CC for JS code is nontrivial. A common approach for other languages is to simply count branching keywords. That doesn't give anything like the the full picture in JS since many common control structures are instead expressed as function calls. Consider:

for (var i = 0; i < 5; i++) {
    /* ... */
}

vs

[0, 1, 2, 3, 4].forEach(function (i) {
    /* ... */
});

Any tool that doesn't recognize those as the same structure is broken. Likewise:

someEventEmitter.on('something', function (d) {
    /* ... */
}).on('error', function (e) {
    /* ... */
});

Not to mention:

someEventEmitter.on('something', declaredElsewhere)
    .on('error', alsoDeclaredElseWhere);

That last case isn't handled well by yardstick either...

License

MIT