Port proverb exercise from JavaScript track

[rchavarria]

As part of the job to make the track compatible with Nextercism, we identified there are missing exercises in this track that are present in the JavaScript track. One of them is proverb.

The task would be to add the proverb exercise to this track, copying files from the JavaScript track and adapting the code to the ECMAScript 6 standard.

Basic steps would include:

1. Copy all files from <javascript repo>/exercises/proverb (https://github.com/exercism/javascript) to <ecmascript repo>/exercises/proverb (https://github.com/exercism/ecmascript)
2. Copy the main package.json file (it's in the root folder of the ecmascript repo https://github.com/exercism/ecmascript/blob/master/package.json) to the <ecmascript repo>/exercises/proverb folder
3. Adapt the code in proverb.spec.js file to use ECMAScript 6 features (import modules, arrow functions, const and/or let, any other feature you think will make the code better). Additionally, the JavaScript track uses Jasmine where the ECMAScript track uses Jest. So, it and xit must be translated to test and xtest. Feel free to adapt example.js as well, just for fun (as long as tests pass)
4. In the README.md of the exercise, replace sections from Setup and below (Setup, Making the test suite pass, Source and Submitting incomplete solutions) with similar sections from any ECMAScript exercise, for example accumulate README. They'll include Setup, Requirements, Making the test suite pass, Source and Submitting incomplete solutions.
5. Copy some exercise information from JavaScript config.json file to the ECMAScript config.json file. This information is an object in the exercises array property with a slug property equals to proverb. Copy that object and place it in the same (or most similar) position in the ECMAScript config.json file. Both config.json files are in the root folder of the repo.

@exercism/ecmascripts - Do you miss something here?

[skabbass1]

@rchavarria @matthewmorgan
There does not seem to be a canonical test file for this exercise set. Is there a reason for that? Would it suffice to just port over the tests currently in the javascript version of the exercise?

[matthewmorgan]

@skabbass1 if's there's no canonical file, porting the javascript tests would make sense.

I think the last test ("test the proverb is the same each time") should be implemented differently though. It happens that in the example implementation in javascript, the toString() method rebuilds the entire output from the inputs each time it's called.

My feeling is that it would be better to make two different Proverb objects, and compare their output.

It might be nice if you could implement a solution that doesn't rely on `bind, which, while idiomatic javascript, is IMO arcane and hard to follow.

@rchavarria ?

[skabbass1]

@matthewmorgan Agree that the current solution is a bit hard to follow. I will refactor and then we can review if it makes sense.

[matthewmorgan]

@skabbass1 great. I think with the ES6 () =>, you would easily be able to eliminate the bind() usage.

Improvements are always good!

[rchavarria]

Yep. I usually find bind and apply usages a bit hard to read and understand. If there is a simpler solution, I favor the simple one.

Great work @skabbass1!

[apapirovski]

This should probably be closed so someone doesn't accidentally work on it. :)

[joeljuca]

Closed by #340.