Core API

[bnjmnt4n]

Just briefly glancing through the “Core” and “More” functions, I think difference and intersection should be in the core, as they are used very commonly.

[chicoxyzzy]

totally agree

[jashkenas]

Are they really? Enlighten us. Got some examples of places you use difference and intersection in real-world code?

[jdalton]

Yep, I those set methods are pretty common (I use them in my own code regularly).

[megawac]

My thoughts on the current state

Strongly in favour of

+indexOf
+lastIndexOf
+now
+omit
+max
+min
+drop
+take
+first
+last
+restParam
+negate

If we're sharing core features and keeping both project identities for now (#6)

-chain
-iteratee

Borderline. I'm not sure if these belong

+union
+intersection
+difference
-memoize
-compose

[akre54]

first and last really? I think I've only used them while chaining. I almost always just do arr[0] or arr[arr.length - 1]. Not pretty, but idiomatic (and makes me wistful for other rubyisms).

Memoize is much better handled in idiomatic JS (the Underscore API isn't great for it). compose is cool, but also not super useful as an API.

[megawac]

They're convenient for cases where arr can be null

[akre54]

How often do you use them outside of chaining though? I'd wager you almost always want to do arr && arr[0] instead. Utility functions are great, using the language is better.

[jridgewell]

I actually use first and last frequently (just for 1 element, not the n form).

Agree with removing memoize and compose, and everything in your "strong support" except negate.

[jdalton]

I actually use first and last frequently (just for 1 element, not the n form).

Lodash split first, last into take, drop, takeWhile, takeRightWhile, dropWhile, dropRightWhile. So the first, last, initial, rest are the most basic forms.

Since the goal is a small core we should err on the side of less, it can always expand later (if needed).

Yep, I those set methods are pretty common (I use them in my own code regularly).

To my earlier comment while difference, intersection, & uniq are handy. Lodash & Underscore differ on implementations so may be easier to punt them as non-core for now.

[jdalton]

Update:
I'm kicking around a combo of methods roughly (give or take a few) like those from Underscore 1.3.3 and Lodash 0.1.0 which comes in at a low 4kb or 5kb.

Update:
Experimenting with a core that can pass the Backbone unit tests.

Updates (July 15):
The following is a list of work items I've done in prepping for lodash v4 (due at the end of July) which proofs out several Underdash ideas.

• Removed the following aliases:
  all, any, backflow, collect, compose, contains, detect, eq, foldl, foldr, head, include, inject, methods, object, select, tail, unique
• Removed _.findWhere, _.pluck, & _.where in favor of _.find, _.map, & _.filter
• Absorbed _.sortByAll into _.sortBy
• Made _.assign, _.extend, _.defaults, & _.merge coerce values to objects so
  _.extend(null,{a:1},{b:2}) will return {a:1,b:2}
• Made "Collection" methods treat functions as objects
• Made _.eq its own method to perform a SameValueZero comparison between two values
• Made _.extend and _.defaults align with Underscore's behavior
• Made _.sortByOrder accept "asc" and "desc" (in v3.10.0)
• Removed IE 6/7 testing
• Removed legacy support for boolean values for options object params in methods like _.debounce
• Removed pre-es5 environment support as those wanting older enviros can simply load es5-shim first
• Removed isDeep params from _.clone and _.flatten in favour of _.cloneDeep and _.flattenDeep
• Removed thisArg, aka context, params methods in favor of folks using _.bind
• Renamed _.callback to _.iteratee to align with Underscore
• Split out _.max, _.min, _.sum, _.sortedIndex, _.sortedLastIndex, _.uniq
  to separate their iteratee functionality with _.maxBy, _.minBy, etc. and limited the iteratee to receive only the value param
• Split out _.assign, _.clone, _.extend, _.isEqual, _.merge, _.omit, & _.pick
  to separate their customizer functionality into _.assignWith, _.cloneWith, etc.
• Removed most of the createXYZ methods for improved readability

Next up I'm creating the smaller core. As for the smaller core I'm currently keeping things as-is for the npm package. This means kitchen sink and modules as usual for node folks. The smaller core build will come in to play for the bower/component packages and site downloads.

[SimenB]

Removed isDeep params from _.clone and _.flatten

Will those still be available in some form? The reason I went from underscore to lodash in the first place was deep clone. 😆 Maybe not the main reason I migrated (jQuery.extend can be made deep), but it was the reason I looked into migrating at all.
(It showed up when I googled why _.clone didn't work like I wanted it to)

Either way, I'm really excited about where you're taking this, keep up the awesome work!

[megawac]

Will those still be available in some form?

_.cloneDeep & _.flattenDeep

[SimenB]

Ah, nice! Never was a fan of boolean params anyway. Perfect solution. Thanks for the swift response! No idea how I didn't notice it before...