Feature: Support for ES6 Lambda in JS API

[AdamBrodzinski]

I'm just starting out and I noticed how awesome the API is. I think it would be an awesome feature if you could match the Python syntax.

example:

    // in JavaScript
    r.table('users').filter(user => user.age > 30).run(conn, callback)

    // instead of 
    r.table('users').filter(r.row('age').gt(30)).run(conn, callback)

   // python eq.
    r.table('users').filter(lambda user: user['age'] > 30).run(conn)

[danielmewes]

I think this should already work, with one small modification:

r.table('users').filter(user => user('age').gt(30)).run(conn, callback)

We cannot overload the > operator in JavaScript, because it doesn't support operator overloading (we use operator overloading in the Python and Ruby drivers to enable this syntax). As far as I know that's still true in ES6.

There seems to be a way to turn user.age into user('age') in ES6 using proxy objects (I found this SO thread on the topic http://stackoverflow.com/questions/20147081/javascript-catch-access-to-property-of-object ). I'm not sure how well it would work in practice, because we would have to make sure that all ReQL commands can still be called on a query object without being turned into a getField call. But it sounds worth considering.

[neumino]

I tried in rethinkdbdash to use ES6 proxy go replace the bracket term with a dot. It's actually surprisingly tricky to do. I ran into tons of issues.

[marshall007]

@danielmewes like @neumino said we were working on exactly this over in neumino/rethinkdbdash#95. The only real issue I ran into was after wrapping Term in a Proxy object I could no longer get those objects to pass instanceof Term checks.

It's really awesome to use, though. If someone can figure that part out I think we should definitely do it in the official driver.

[neumino]

Yea I had this issue with instanceof. I patched by adding a new method like _isTerm. But then I ran into other issues like Object.keys(<proxy>), <proxy>.hasOwnProperty, JSON.stringify etc. Every time I was patching something, another issue was coming up.

It's probably doable, but it's just a bit tedious I think.

[deontologician]

Since lambdas work and operator overloading isn't possible yet. I think we should close this issue. The bracket syntax vs. attribute syntax seems nice, but that wasn't in the original request. I have some qualms about the attribute syntax, but I think we should open a new issue for that if it's something people want.

[danielmewes]

Ok let's keep an eye on the dot syntax for field access (though it seems difficult enough that it's probably not worth doing at the moment). Closing this.

[AdamBrodzinski]

Sounds good to me. Thanks for all the feedback!

[deontologician]

@AdamBrodzinski I just remembered, if you're really interested in infix operators for js, I wrote a small sweet.js preprocessor that works (mostly, there are lots of edge cases): https://gist.github.com/deontologician/e65923823e0c3111c880

[AdamBrodzinski]

@deontologician cool i'll check it out!