Static Methods

fromArray

Takes a normal JavaScript array and turns it into a Sequence of the same type.
Usage
Type Definition
const sequence: Seq<number> = fromArray([1, 2, 3]);
type fromArray<T> = (data: T[]) => Seq<T>;

iterate

The iterate method simplifies the construction of infinite sequences which are built using their previous value.
Usage
Type Definition
// Builds an infinite sequence that counts up from 0.
const sequence: Seq<number> = iterate(a => a + 1, 0);
type iterate = <T>(fn: (current: T) => T, start: T): Seq<T>

fib

The fib method generates a sequence of fibonacci numbers.
Usage
Type Definition
const sequence: Seq<number> = fib();
type fib = () => Seq<number>;

random

Generates a random sequence using Math.random.
Usage
Type Definition
// Builds sequence of random numbers between 0 and 1.
const sequence: Seq<number> = random();
type random = () => Seq<number>;

range

Creates a sequence that counts between a start and end value. Takes an optional step parameter.
Usage
Type Definition
// Step by 1 from 0 through 10.
const sequence: Seq<number> = range(0, 10);
// Step by 1 from 0 through Infinity.
const sequence: Seq<number> = range(0, Infinity);
// Step by 1 from -10 through +10.
const sequence: Seq<number> = range(-10, 10);
// Step down from +10 through -10.
const sequence: Seq<number> = range(10, -10);
// Step by 2 from 0 through 10.
const sequence: Seq<number> = range(0, 10, 2);
type range(
start: number,
end: number,
step = 1
) => Seq<number>;

infinite

A sequence that counts from 0 to Infinity.
Usage
Type Definition
const sequence: Seq<number> = infinite();
type infinite = () => Seq<number>;

of

A sequence with only a single value inside. Also known as "singleton."
Usage
Type Definition
const sequence: Seq<number> = of(2);
type of = <T>(...values: T[]): Seq<T>;

cycle

Create a sequence that is the infinite repetition of a series of values.
Usage
Type Definition
const sequence: Seq<string> = cycle(["a", "b", "c"]);
type cycle = <T>(items: T[]) => Seq<T>;

repeat

Create a sequence which repeats the same value X number of times. The length of the sequence defaults to Infinity.
Usage
Type Definition
// Creates a sequence of 5 true values.
const sequence: Seq<boolean> = repeat(true, 5);
// Creates a sequence of 0 which repeats infinitely.
const sequence: Seq<number> = repeat(0);
type repeat = <T>(value: T, times = Infinity) => Seq<T>;

repeatedly

Creates a sequence which pulls from an impure callback to generate the sequence. The second parameter can cap the length of the sequence. By default, it will call the callback infinitely to generate values. Useful for asking about current time or cache values.
Usage
Type Definition
const sequence: Seq<Date> = repeatedly(() => new Date());
type repeatedly = <T>(value: () => T, times = Infinity) => Seq<T>;

empty

A sequence with nothing in it. Useful as a "no op" for certain code-paths when joining sequences together.
Usage
Type Definition
const sequence: Seq<never> = empty();
type empty = () => Seq<never>;

zip

Takes two sequences and lazily combines them to produce a tuple with the current step in each of the two positions. Useful for zipping a sequence of keys with a sequence of values, before converting to a Map of key to value.
Usage
Type Definition
const seq1 = fromArray(["zero", "one", "two", "three"]);
const seq2 = range(0, 3);
// Gives: ["zero", 0] -> ["one", 1] -> ["two", 2] -> ["three", 3]
const sequence: Seq<[string, number]> = zip(seq1, seq2);
type zip = <T1, T2>(
seq1: Seq<T1>,
seq2: Seq<T2>
) => Seq<[T1 | undefined, T2 | undefined]>;

zipWith

Takes two sequences and lazily combines them to produce an arbitrary value by mapping the current value of the two positions through a user-supplied function. Useful for table (row/col) math.
Usage
Type Definition
const seq1 = range(0, 3);
const seq2 = repeat(2);
// Gives: 0 -> 2 -> 4 -> 6
const sequence: Seq<number> = zipWith(
([num, multiplier]) => num * multiplier,
seq1,
seq2
);
type zipWith = <T1, T2, T3>(
fn: (
[result1, result2]: [T1, T2] | [T1, undefined] | [undefined, T2],
index: number
) => T3,
seq1: Seq<T1>,
seq2: Seq<T2>
) => Seq<T3>;

zip3

Takes three sequences and lazily combines them to produce a 3-tuple with the current step in each of the three positions.
Usage
Type Definition
const seq1 = fromArray(["zero", "one", "two", "three"]);
const seq2 = range(0, 3);
const seq3 = range(3, 0);
// Gives: ["zero", 0, 3] -> ["one", 1, 2] -> ["two", 2, 1] -> ["three", 3, 0]
const sequence: Seq<[string, number]> = zip3(seq1, seq2, seq3);
type zip3 = <T1, T2, T3>(
seq1: Seq<T1>,
seq2: Seq<T2>,
seq3: Seq<T3>
) => Seq<[T1 | undefined, T2 | undefined, T3 | undefined]>;

zip3With

Takes three sequences and lazily combines them to produce an arbitrary value by mapping the current value of the three positions through a user-supplied function.
Usage
Type Definition
const seq1 = range(0, 3);
const seq2 = repeat(2);
const seq3 = repeat(1);
// Gives: 0 -> 2 -> 4 -> 6
const sequence: Seq<number> = zip3With(
([num, multiplier, divisor]) => (num * multiplier) / divisor,
seq1,
seq2,
seq3
);
type zip3With = <T1, T2, T3, T4>(
fn: (
[result1, result2, resul3]:
| [T1, T2, T3]
| [T1, undefined, undefined]
| [T1, T2, undefined]
| [T1, undefined, T3]
| [undefined, T2, undefined]
| [undefined, T2, T3]
| [undefined, undefined, T3],
index: number
) => T4,
seq1: Seq<T1>,
seq2: Seq<T2>,
seq3: Seq<T3>
) => Seq<T4>;

concat

Combines 2 or more sequences into a single sequence.
Usage
Type Definition
const sequence: Seq<number> = concat(
fromArray([0, 1]),
fromArray([2, 3]),
fromArray([4, 5])
);
type concat = <T>(...items: Array<Seq<T>>) => Seq<T>;

interleave

Takes 2 or more sequences and creates a new sequence built by pulling the next value from each of the sequences in order.
Usage
Type Definition
// Builds: a -> 1 -> b -> 2 -> c -> 3
const sequence: Seq<string | number> = interleave(
fromArray(["a", "b", "c"]),
range(1, 3)
);
type interleave = <T>(...items: Array<Seq<T>>) => Seq<T>;
Copy link
On this page
fromArray
iterate
fib
random
range
infinite
of
cycle
repeat
repeatedly
empty
zip
zipWith
zip3
zip3With
concat
interleave