map

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2023-12-01

Creates a new sequence whose values are calculated by passing this sequence's elements through some mapping function.

Signature

Sequence.map = function(mapFn) { /*...*/ }

Sequence.map = function map(mapFn) {
  return new MappedSequence(this, createCallback(mapFn));
}

Name	Type(s)	Description
mapFn	Function	The mapping function used to project this sequence's elements onto a new sequence. This function takes up to two arguments: the element, and the current index.
returns	Sequence	The new sequence.

Examples

function addIndexToValue(e, i) { return e + i; }

Lazy([]).map(increment)              // sequence: []
Lazy([1, 2, 3]).map(increment)       // sequence: [2, 3, 4]
Lazy([1, 2, 3]).map(addIndexToValue) // sequence: [1, 3, 5]

Benchmarks

function increment(x) { return x + 1; }

var smArr = Lazy.range(10).toArray(),
lgArr = Lazy.range(100).toArray();

Lazy(smArr).map(increment).each(Lazy.noop) // lazy - 10 elements
Lazy(lgArr).map(increment).each(Lazy.noop) // lazy - 100 elements
_.each(_.map(smArr, increment), _.noop)    // lodash - 10 elements
_.each(_.map(lgArr, increment), _.noop)    // lodash - 100 elements

Implementation	10 elements	100 elements
lazy
lodash