underscore.array

An addition to the awesome underscore project, focusing on arrays.

Defined functions.

groupby(array, [iterator], [context])

Returns an array of arrays where consecutive elements are grouped by the iterator. If iterator is not supplied, identity is used instead. If iterator is a number, the array will be grouped into arrays of size iterator, with the last array potentially being less than size iterator. The iterator function will be passed both the element, and its index in the array.

_.groupby([1, 2, 3, 4, 5, 6, 7], 3); 
// => [[1, 2, 3], [4, 5, 6], [7]]

_.groupby([1, 2, 3, 4, 5, 6, 7], function (a, i) {
   return a < 4;
});
// => [[1, 2, 3], [4, 5, 6, 7]]

partition(array, iterator, [context])

Divides the array into two arrays determined by the results of iterator. If iterator returns a truthy value, it goes in the first array, otherwise, it goes into the second array.

_.partition([1, 5, 2, 6, 3, 7, 4], function (a) { return a < 4; });
// => [[1, 2, 3], [5, 6, 7, 4]]

applyTo(array, function, [context])

Call function.apply(context, array). Useful for chained invocations (The underscore project must be included to use chained invocations).

var results = []
_.applyTo([1, 2, 3], results.push, results);
// results == [1, 2, 3]

mapApply(arrayOfArrays, iterator, [context])

Applies each array to iterator, returning the array of results. Useful after a groupby call.

_.mapApply([[1, 2], [3, 4]], function (a, b) { return a + b;})
// => [3, 4]

binarySearch(sortedArray, iterator, [context])

Given a sorted array, will find the element matching iterator. The iterator should return < 1 to go left, truthy to go right and falsy on match. If iterator is not a function, will use binarySearch.naturalCompare(iterator)

binarySearch.naturalCompare(x) will return an iterator that uses a types natural ordering to adhere to the above contract;