sortBy

SortBy is a function name used in several JavaScript utility libraries to produce a new array sorted according to one or more computed keys rather than the elements themselves. The most common implementations come from libraries such as Lodash and Underscore. It does not modify the input collection; instead it returns a new, sorted array.

In typical usage, sortBy takes a collection (array or array-like) and one or more iteratees that specify how to derive the sort key from each element. Each iteratee can be a function that returns a value, or a string naming a property of the element. The array is then sorted in ascending order of the computed keys. If multiple iteratees are provided, sorting uses the first key, then resolves ties using the second, and so on.

Common examples (in a Lodash-like style): sortBy(users, 'age') sorts by age in ascending order; sortBy(items, [getPriority, 'name']) sorts by getPriority results first, then by name. Note that some libraries provide a separate function orderBy to control ascending/descending per key.

A note: sortBy usually returns a new array and does not mutate the original one. The exact behavior for stability and tie-breaking can vary by library version, so consult the specific implementation’s documentation for guarantees.

See also: sort, orderBy, comparator, key extractor.