Discussion on: Practical Functional Programming in JavaScript - Control Flow

[Functional Javascript]

Great stuff Richard.
And great community input David.

Congrats on the Rubico library also. Keep at 'er.

I notice you have a bunch of posts on dev.to on your functional approach, so over the next little while I'll take a gander through them.

I've only read this post of yours so far, so I'm not commenting on your full body of work, but let me compare with my architectural viewpoint of a functional approach to software architecture.

As far as how things are implemented I care about these attribute, in this order...

• natural language documentation
• security
• robustness
• performance
• code readability

More can be said on how those attributes interplay, but the actual implementation that gets chosen is the one that wins out on that prioritized attribute set.

So from your examples above, none of those won out. :)
I'd use the switch statement, as it uses 10 to 20 times less cycles.

After running each func 1e+6 (1 million) times....

Func	Time	Iter
cliSwitch	24.255ms	1e6
cliSwitchIncludes	46.474ms	1e6
cliIf	224.728ms	1e6
cliTernary	242.144ms	1e6
cliRubico	413.755ms	1e6

/**
@func
test switching through a set of possible flags
- input by the user from the cli

@param {string[]} args - contains the passed-in flag
*/
const cliSwitch = args => {
  const s = args[2];
   switch (s) {
    case "-h":
    case "--help":
      l('usage: ./cli [-h] [--help] [-v] [--version]');
      break;
    case "-v":
    case "--version":
      l('v0.0.1');
      break;
    default:
      l('unrecognized command');
  }
};

//@tests
timeInLoop("cliSwitch", 1e6, () => cliSwitch(["", "", "-nomatch"]));

Source Code for the timeInLoop func:

gist.github.com/funfunction/91b587...

[Richard Tong]

could you elaborate on natural language documentation?

[Functional Javascript]

Hey Richard,

I just posted an article to elaborate on that...
dev.to/functional_js/squeezing-out...

[Functional Javascript]

Hey Richard,

That isPromise check should be fast.
I think your bottleneck there will be the recursion idiom.
The iterative idiom is always faster and more robust.
Any recursion can be replaced with a simple loop.
(I never use recursion, it always fails my robustness and performance tests)

However

However your non-recursive "or" func is slow verses the baseline, and so is its utility, "arrayOr", even when I pass in non-promises (which should make it take the fastest path).

const arrayOr = (fns, x) => {
  const promises = []
  for (let i = 0; i < fns.length; i++) {
    const point = fns[i](x)
    if (isPromise(point)) promises.push(point)
    else if (point) return (promises.length > 0
      ? Promise.all(promises).then(() => true)
      : true)
  }
  return (promises.length > 0
    ? Promise.all(promises).then(res => res.some(x => x))
    : false)
}

//@tests
timeInLoop("arrayOr", 1e6, () => arrayOr([() => 1, () => 2, () => 3], 0)) //48.216ms for 1e6

isPromise

Btw, as a little aside, I perf-compared your isPromise implementation with mine.
Now, my isPromise looks more "proper"; and is actually more robust in my robustness test (not shown here), however yours is magnificently faster, by almost 10x :-) ...

const isPromise = v => v instanceof Promise;

const isPromise2 = x => x && typeof x.then === "function"

//@tests
const aFalse = [undefined, e => e, {}, { then: {}}, {then: e => e}];
//const aTrue = [new Promise(resolve => { }), new Promise(e => e)];
timeInLoop("isPromise", 1e6, () => isPromise(aFalse)); //93.021ms
timeInLoop("isPromise2", 1e6, () => isPromise2(aFalse)); //10.004ms

prioritized attribute set

So using my "prioritized attribute set" criteria explained in my first post, if I can modify yours enough to be as robust as mine (should be easy to do with very little performance hit) I will swap the slow for the fast.

[Functional Javascript]

Nice!

Feel free to post the source code and I'll give it a shot myself.

And yes, as I had mentioned in the Tips section of the Post I linked to above, each test must be run separately, otherwise the compiler may optimize some code by learning from the other code.

[Richard Tong]

switchCase benchmarks here: github.com/a-synchronous/rubico/bl...

[Functional Javascript]

I think the problem with your code might be that your second "switchCase" is running with a lamba inside of a lamba, so the actual code you want to test does not get hit.
Correct me if I'm wrong.

Here are my results...
It includes the test of the buggy one.

Note:
I ran each "timeInLoop" separately, and about 5 times each, and reported the lowest score.

import { or, switchCase } from "rubico";
import timeInLoop from "./timeInLoop";

const isOdd = x => x % 2 === 1;


//@perftests

//isOdd: 1e+6: 10.013ms
timeInLoop("isOdd", 1e6, () => isOdd(4));



// isOdd_ternary: 1e+6: 9.726ms
timeInLoop("isOdd_ternary", 1e6, () => {
  isOdd(4) ? 1 : 0
});


// isOdd_ifElse: 1e+6: 9.846ms
timeInLoop("isOdd_ifElse", 1e6, () => {
  if (isOdd(4)) return 'odd'
  else return 'even'
});


// isOdd_switch: 1e+6: 9.776ms
timeInLoop("isOdd_switch", 1e6, () => {
  switch (isOdd(4)) {
    case true: return 'odd'
    default: return 'even'
  }
});



//isOdd_rubicoSwitchCase: 1e+6: 152.762ms
timeInLoop("isOdd_rubicoSwitchCase", 1e6, () => {
  switchCase([() => isOdd(4), () => 'odd', () => 'even'])
});



//@BUG: a nested lambda, the code to be perftested never executes
// isOdd_rubicoSwitchCaseExtraLambda: 1e+6: 10.667ms
timeInLoop("isOdd_rubicoSwitchCaseExtraLambda", 1e6, () => {
  () => switchCase([isOdd, () => 'odd', () => 'even'])
});

[Richard Tong]

I looked into it a bit, turns out the differences we were seeing were due to mocha. I was using it to organize the benchmarks, but I see now that I should probably get closer to the ground. I'll also revise rubico's timeInLoop to model yours more closely.

[Functional Javascript]

Great.
Keep up the good work, and let me know how it progresses and if you come up with more ideas.