sortBy

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2023-12-01

Creates a new sequence with the same elements as this one, but ordered by the results of the given function.

You can pass:

a string, to sort by the named property
a function, to sort by the result of calling the function on each element

Signature

Sequence.sortBy = function(sortFn, descending) { /*...*/ }

Sequence.sortBy = function sortBy(sortFn, descending) {
  sortFn = createComparator(sortFn);
  if (descending) { sortFn = reverseArguments(sortFn); }
  return new SortedSequence(this, sortFn);
}

Name	Type(s)	Description
sortFn	Function	The function to call on the elements in this sequence, in order to sort them.
descending	boolean	Whether or not the resulting sequence should be in descending order (defaults to `false`).
returns	Sequence	The new sequence.

Examples

function population(country) {
  return country.pop;
}

function area(country) {
  return country.sqkm;
}

var countries = [
  { name: "USA", pop: 320000000, sqkm: 9600000 },
  { name: "Brazil", pop: 194000000, sqkm: 8500000 },
  { name: "Nigeria", pop: 174000000, sqkm: 924000 },
  { name: "China", pop: 1350000000, sqkm: 9700000 },
  { name: "Russia", pop: 143000000, sqkm: 17000000 },
  { name: "Australia", pop: 23000000, sqkm: 7700000 }
];

Lazy(countries).sortBy(population).last(3).pluck('name') // sequence: ["Brazil", "USA", "China"]
Lazy(countries).sortBy(area).last(3).pluck('name')       // sequence: ["USA", "China", "Russia"]
Lazy(countries).sortBy(area, true).first(3).pluck('name') // sequence: ["Russia", "China", "USA"]

Benchmarks

var randoms = Lazy.generate(Math.random).take(100).toArray();

Lazy(randoms).sortBy(Lazy.identity).each(Lazy.noop) // lazy
_.each(_.sortBy(randoms, Lazy.identity), _.noop)    // lodash

Implementation	Ops/second
lazy
lodash