Hacker News Reader

Comment by javajosh | Hacker News Reader

There's no doubt this is a nice little library. There's also no doubt that I won't use it. Why? Because all the neat stuff in this library is available with Underscore, and Underscore works with plain vanilla arrays.

It might be possible for a library like this to really catch on so much that a) other people use it, and b) even when they don't you get so much power you don't mind typing array(someOtherRealArray) all the time. JodaTime is like that.

But the thing that JodaTime has that Array.js doesn't is an enemy. JodaTime hates the built in Date, Calendar, etc classes in the JDK. It hates them and replaces them with extreme prejudice, and anyone forced to work with those APIs does not weep.

Array.js does not have an enemy, it has a friend it wants to help be a little better. It's a nice library, a helpful library. And that's why it will soon be forgotten, I'm afraid.

View on HN

(disclosure, I work on Underscore)

I think this is a pretty neat approach. It would be fun to play around with a version of Underscore that implemented a version of the idea. I make take a crack at it...

Creating a new datatype would pretty seriously go against Underscore's implicit philosophy of being a set of functions you bring to bear on ordinary data structures. In other words, you can try, but I suspect your pull request be voted down fairly decisively.

EDIT: apparently you are the creator of Underscore. Which makes me feel sort of silly for saying at least the second part. I think the first part stands, however.

Probably, but I'm thinking that it might be an approach worth taking a look at as an alternative to the current:

    _.chain(array).map(func).filter(func).reduce(func).value()

Taking a look at returning an array-like (or object-like, depending on what you pass in), for that same use case:

    _(array).map(func).filter(func).reduce(func)

... could be nice. The devil's in the details of interoperability with other libraries, as other folks note in this thread.

> The devil's in the details of interoperability with other libraries, as other folks note in this thread.

Indeed. I should have also mentioned that editing angular.js to work is fairly straightforward (~5-10 LOC), and this is probably fairly typical. So if you are willing to patch this isn't necessarily a blocker, and done right could probably be submitted as a reasonable merge request.

So in order to save one call to chain() you'd use a non-standard object over a native array? What would underscore methods return, then? Perhaps it could do type detection and return what it gets, but then you have the issue that the executing code needs to be aware of that too - which means a type check at the caller before invoking the underscore expression. Needless to say, I think that's a lot of added complexity for not a lot of benefit.

Heck, if you really wanted to adapt something from Array.js you could do the naive (but I think correct) thing which is to add a flag to all underscore methods indicating whether or not the method should return an "Underscored" object or the basic data type. This could even be an initialization parameter for Underscore.

What does this buy you? I can only think of two things. First is they get a more object-oriented feel to their code.

    var foo = _.filter([1,2,3], func, true);
    // later on...
    foo.filter(func2);

I guess the first question I have is, what does line 3 do? Are we mutating foo? Or returning something new? In which case we've managed to save precisely one character

     _.filter(foo, func2);

Even worse, we're saving the wrong character. One undersung quality of having one global object per major library is that, in the code, you get a big contextual clue about what's going on from the way it's invoked. Contrast these two lines:

    foo.filter(func2);
    _.filter(foo, func2);

Try to imagine that you're encountering these lines deep in the bowels of the code. Which one is easier to understand?

The second thing you get is a (what I think is) esoteric benefit of being able to "ship" underscore functionality with the data to far away places. This is only an issue in full require()-controlled programs where there might be some communication between closures, and one side wants to use underscore in that context, but not add a dependency. Personally, I think being able to do that is just asking for trouble, as, again, your calling code maintainers are going to be totally befuddled by running into objects doing things that no other objects in that side are doing - or worse, doing something that looks familiar, but isn't.

You're saving at least two characters there ;)

I think sensible semantic naming still helps in this circumstance.

    yummyBars = candyBars.filter(function(bar){ return bar.yummy; });

makes it clearer that the thing you're getting back is like the thing you had previously.

One place this could be useful is in Backbone.Collection where the array-returning mixins from underscore all hand back bare arrays, on which devs must then switch to _ prefixed functions (although you're right that this does keep a clear conceptual separation between collections and other arrays).

I get a warm and fuzzy when I know what that method does, that it's not some random filter that could mean something totally different. (And yes, this does mean that my code is not very object oriented at all!)

That's okay! Use the right tool in the right place. And agreed, I like knowing where a function comes from.

I'm not totally convinced by the move to 100% functionalist constructs (there are some places where OO is nice), but it's a nice stylistic practice.

It has one important downside tho - because you can't chain calls, your code ends up much less readable: It needs to be read from the inside-out, and the functions you're applying on the array are in reverse order compared to the order of execution. Its also harder to to see which arguments go to which function.

Compare

    _(array).map(func).filter(func).reduce(func)

and:

   _.reduce(_.filter(_.map(array, func), func), func)

jashkenas is being humble. He's actually the creator of underscore (and backbone, and coffeescript, and docco...).

This is where I point out that the idea of jashkenas getting a pull request rejected from Underscore would be pretty funny.

Not that it couldn't happen, of course, I don't know if he still is in charge or not. But it'd be amusing.

Yeah, as far as i'm concerned, jashkenas is still BDFL for DocumentCloud's major libraries.

I've taken over maintenance of the main DocumentCloud platform and document viewer repos, as well as docsplit.

And although I've been shirking on jammit, but I intend to cut a new version of the gem soon.

The way I did it was to write lots of functions that take e.g. an array (the same approach works for other things) as their first argument, then a function that I called unbind which converts a function of x arguments into a function of (x-1) arguments where the first argument is replaced with the this pointer. Then you can have a function ('bless') that copies all of those 'unbound' functions onto a real data object or prototype. That way you get the best of both worlds and it's up to the user as to what they bless.

The other aspect to this of course is that using es6 proxies, the library could have been made to behave exactly like the native array even without using one.

I would love to see underscore integrate this style of API.

This involves a lot "String Programming" which makes code hard to test and debug.

user.max("age"); looks sexy but I'm sure type of error you get from user.max(func)l is much better and more clear

I do like how the `select` can take a string, "x > 30", vs a function(x){ return x > 30}

It would be be nice if Underscore had a bit more sugar like that. But, I also know how problematic it can be to properly parse or evaluate a string into code.

--edit--

it is using the to-function library to do this: https://github.com/component/to-function

Passing it in as a string just feels dirty to me for some reason.

It feels dirty to me too, because of the possible "filter injections", similar to the SQL-injection flaws.

It's also likely to be inherently hard to optimize; aka slow and will stay slow. I thinks it's a generally bad idea. It also undermines what limited tooling there is for JS; and it exposes Yet Another set of semantics - what exactly does that query do, how is it translated, what are the corner cases etc.

Very Bad idea. (And for what - avoiding a few characters that are so common as to be trivially skimmable and very gzippable?)

What do you think about jquery selectors? Do the same objections apply?

CSS selectors also give me this bad feeling when used in javascript code.

I think they do too. I used to fall-back to vanilla DOM queries sometimes when I started using jQuery, because it didn't feel quite right, and I always worried about the performance hit... but I ended up always using CSS selectors, unless there's a good reason not to.

I think the main difference is that the value proposition of CSS selectors is just better than of the string-function syntax, so its worth it.

If you care about minor syntactical details like that, you should already be using coffeescript:

    select((o) -> o.x > 30)

Seriously, it's great. :)

Didn't understand all the JodaTime references, but as far as your main point, this library is doing the same things that underscore is doing - wrapping an array. Consider: _(['apple', 'orange', 'pear']).map(fn);

You could just as easily approach this lib the same way: array(['apple', 'orange', 'pear']).map(fn);

The only difference with this library and other arrays/client-side collections I've come across is that there's less indirection, which I find less confusing, ie. am I working with a collection object or am I working with an array?

Of course there are caveats (things to consider) when using this lib which I outlined in the docs.

I agree with you here; I usually have underscored included in both the server and browser for my projects. Events seem like it could be useful. Sure Backbone gives you events on models and collections, but I don't always include Backbone models in my node apps.

Reply on news.ycombinator.com