immutable - npm Package Compare versions

Comparing version 4.1.0 to 4.2.0

package.json

 {
   "name": "immutable",
-  "version": "4.1.0",
+  "version": "4.2.0",
   "description": "Immutable Data Collections",
@@ -5,0 +5,0 @@ "license": "MIT",

README.md

@@ -640,2 +640,42 @@ # Immutable collections for JavaScript
 
+## Comparison of filter(), groupBy(), and partition()
+
+The `filter()`, `groupBy()`, and `partition()` methods are similar in that they
+all divide a collection into parts based on applying a function to each element.
+All three call the predicate or grouping function once for each item in the
+input collection.  All three return zero or more collections of the same type as
+their input.  The returned collections are always distinct from the input
+(according to `===`), even if the contents are identical.
+
+Of these methods, `filter()` is the only one that is lazy and the only one which
+discards items from the input collection. It is the simplest to use, and the
+fact that it returns exactly one collection makes it easy to combine with other
+methods to form a pipeline of operations.
+
+The `partition()` method is similar to an eager version of `filter()`, but it
+returns two collections; the first contains the items that would have been
+discarded by `filter()`, and the second contains the items that would have been
+kept.  It always returns an array of exactly two collections, which can make it
+easier to use than `groupBy()`.  Compared to making two separate calls to
+`filter()`, `partition()` makes half as many calls it the predicate passed to
+it.
+
+The `groupBy()` method is a more generalized version of `partition()` that can
+group by an arbitrary function rather than just a predicate.  It returns a map
+with zero or more entries, where the keys are the values returned by the
+grouping function, and the values are nonempty collections of the corresponding
+arguments.  Although `groupBy()` is more powerful than `partition()`, it can be
+harder to use because it is not always possible predict in advance how many
+entries the returned map will have and what their keys will be.
+
+| Summary                       | `filter` | `partition` | `groupBy`      |
+|:------------------------------|:---------|:------------|:---------------|
+| ease of use                   | easiest  | moderate    | hardest        |
+| generality                    | least    | moderate    | most           |
+| laziness                      | lazy     | eager       | eager          |
+| # of returned sub-collections | 1        | 2           | 0 or more      |
+| sub-collections may be empty  | yes      | yes         | no             |
+| can discard items             | yes      | no          | no             |
+| wrapping container            | none     | array       | Map/OrderedMap |
+
 ## Additional Tools and Resources
@@ -642,0 +682,0 @@

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Lines of code

16020

increased by1.39%

Number of lines in readme file

758

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