A JavaScript port of Python's awesome itertools standard library.
Usage example:
import { izip, cycle } from 'itertools';
const xs = [1, 2, 3, 4];
const ys = ['hello', 'there'];
for (const [x, y] of izip(xs, cycle(ys))) {
console.log(x, y);
}
// 1 'hello'
// 2 'there'
// 3 'hello'
// 4 'there'In Python, many of the itertools take a function as an argument. In the JS port of these we initially kept these orderings the same to stick closely to the Python functions, but in practice, it turns out to be more pragmatic to flip them, so the function gets to be the second param. Example:
In Python:
map(fn, items)But in JavaScript:
map(items, fn)The rationale for this flipping of argument order is because in practice, the function bodies can span multiple lines, in which case the following block will remaing aesthetically pleasing:
import { map } from 'itertools';
const numbers = [1, 2, 3];
const squares = map(numbers, n => {
//
// Do something wild with these numbers here
//
// ...
return n * n;
});The itertools package consists of a few building blocks:
Returns true when all of the items in iterable are truthy. An optional key function can be used to define what truthiness means for this specific collection.
Examples:
all([]) // => true
all([0]) // => false
all([0, 1, 2]) // => false
all([1, 2, 3]) // => true
Examples with using a key function:
all([2, 4, 6], n => n % 2 === 0) // => true
all([2, 4, 5], n => n % 2 === 0) // => false
Parameters
iterableIterable<T>keyFnPredicate<T> (optional, defaultidentityPredicate)
Returns boolean
Returns true when any of the items in iterable are truthy. An optional key function can be used to define what truthiness means for this specific collection.
Examples:
any([]) // => false
any([0]) // => false
any([0, 1, null, undefined]) // => true
Examples with using a key function:
any([1, 4, 5], n => n % 2 === 0) // => true
any([{name: 'Bob'}, {name: 'Alice'}], person => person.name.startsWith('C')) // => false
Parameters
iterableIterable<T>keyFnPredicate<T> (optional, defaultidentityPredicate)
Returns boolean
Returns true when any of the items in the iterable are equal to the target object.
Examples:
contains([], 'whatever') // => false
contains([3], 42) // => false
contains([3], 3) // => true
contains([0, 1, 2], 2) // => true
Parameters
haystackIterable<T>needleT
Returns boolean
Returns an iterable of enumeration pairs. Iterable must be a sequence, an iterator, or some other object which supports iteration. The elements produced by returns a tuple containing a counter value (starting from 0 by default) and the values obtained from iterating over given iterable.
Example:
import { enumerate } from 'itertools';
console.log([...enumerate(['hello', 'world'])]);
// [0, 'hello'], [1, 'world']]
Parameters
iterableIterable<T>startnumber (optional, default0)
Returns Iterable<[number, T]>
Non-lazy version of ifilter().
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Array<T>
Returns an iterator object for the given iterable. This can be used to manually get an iterator for any iterable datastructure. The purpose and main use case of this function is to get a single iterator (a thing with state, think of it as a "cursor") which can only be consumed once.
Parameters
iterableIterable<T>
Returns Iterator<T>
Non-lazy version of imap().
Parameters
iterableIterable<T>mapperfunction (T): V
Returns Array<V>
Return the largest item in an iterable. Only works for numbers, as ordering
is pretty poorly defined on any other data type in JS. The optional keyFn
argument specifies a one-argument ordering function like that used for
sorted().
If the iterable is empty, undefined is returned.
If multiple items are maximal, the function returns either one of them, but which one is not defined.
Parameters
iterableIterable<T>keyFnfunction (T): number (optional, defaultnumberIdentity)
Returns Maybe<T>
Return the smallest item in an iterable. Only works for numbers, as
ordering is pretty poorly defined on any other data type in JS. The
optional keyFn argument specifies a one-argument ordering function like
that used for sorted().
If the iterable is empty, undefined is returned.
If multiple items are minimal, the function returns either one of them, but which one is not defined.
Parameters
iterableIterable<T>keyFnfunction (T): number (optional, defaultnumberIdentity)
Returns Maybe<T>
TODO
Parameters
Returns Iterable<number>
TODO: Reducer function with a start value.
Parameters
iterableIterable<T>reducerfunction (O, T, number): OstartO
Returns O
TODO: Document Reducer function without a start value. The start value will be the first item in the input iterable. For this reason, the function may not necessarily return anything (i.e. if the input is empty), and the inputs and the outputs must be of homogeneous types.
Parameters
iterableIterable<T>reducerfunction (T, T, number): T
Returns Maybe<T>
TODO
Parameters
iterableIterable<T>keyFnfunction (T): Primitive (optional, defaultprimitiveIdentity)reverseboolean (optional, defaultfalse)
Returns Array<T>
TODO
Parameters
iterableIterable<number>
Returns number
TODO
Parameters
xsIterable<T1>ysIterable<T2>
Returns Array<[T1, T2]>
TODO
Parameters
xsIterable<T1>ysIterable<T2>zsIterable<T3>
Returns Array<[T1, T2, T3]>
Returns an iterator that returns elements from the first iterable until it is exhausted, then proceeds to the next iterable, until all of the iterables are exhausted. Used for treating consecutive sequences as a single sequence.
Parameters
iterables...Array<Iterable<T>>
Returns Iterable<T>
Returns an iterator that counts up values starting with number start
(default 0), incrementing by step. To decrement, use a negative step
number.
Parameters
Returns Iterable<number>
Non-lazy version of icompress().
Parameters
dataIterable<T>selectorsIterable<boolean>
Returns Array<T>
Returns an iterator producing elements from the iterable and saving a copy of each. When the iterable is exhausted, return elements from the saved copy. Repeats indefinitely.
Parameters
iterableIterable<T>
Returns Iterable<T>
Returns an iterator that drops elements from the iterable as long as the predicate is true; afterwards, returns every remaining element. Note, the iterator does not produce any output until the predicate first becomes false.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterator that filters elements from data returning only those
that have a corresponding element in selectors that evaluates to true.
Stops when either the data or selectors iterables has been exhausted.
Parameters
dataIterable<T>selectorsIterable<boolean>
Returns Iterable<T>
Returns an iterator that filters elements from iterable returning only those for which the predicate is true.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterator that computes the given mapper function using arguments from each of the iterables.
Parameters
iterableIterable<T>mapperfunction (T): V
Returns Iterable<V>
Returns an iterator that returns selected elements from the iterable. If
start is non-zero, then elements from the iterable are skipped until start
is reached. Then, elements are returned by making steps of step (defaults
to 1). If set to higher than 1, items will be skipped. If stop is
provided, then iteration continues until the iterator reached that index,
otherwise, the iterable will be fully exhausted. islice() does not
support negative values for start, stop, or step.
Parameters
Returns Iterable<T>
Returns an iterator that aggregates elements from each of the iterables.
Used for lock-step iteration over several iterables at a time. When
iterating over two iterables, use izip2. When iterating over three
iterables, use izip3, etc. izip is an alias for izip2.
Parameters
xsIterable<T1>ysIterable<T2>
Returns Iterable<[T1, T2]>
Like izip2, but for three input iterables.
Parameters
xsIterable<T1>ysIterable<T2>zsIterable<T3>
Returns Iterable<[T1, T2, T3]>
Like the other izip's, but generalized. Due to type system limitations, you can only "generially" zip iterables with homogeneous types, so you cannot mix types like <A, B> like you can with izip2()
Parameters
iters...Array<Iterable<T>>
Returns Iterable<Array<T>>
Return successive r-length permutations of elements in the iterable.
If r is not specified, then r defaults to the length of the iterable and
all possible full-length permutations are generated.
Permutations are emitted in lexicographic sort order. So, if the input iterable is sorted, the permutation tuples will be produced in sorted order.
Elements are treated as unique based on their position, not on their value. So if the input elements are unique, there will be no repeat values in each permutation.
Parameters
iterableIterable<T>rMaybe<number>
Returns Iterable<Array<T>>
Returns an iterator that produces elements from the iterable as long as the predicate is true.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterable containing only the first n elements of the given
iterable.
Parameters
nnumberiterableIterable<T>
Returns Iterable<T>
Non-lazy version of itake().
Parameters
nnumberiterableIterable<T>
Returns Array<T>
Returns an iterator that returns elements from the first iterable until it is exhausted, then proceeds to the next iterable, until all of the iterables are exhausted. Used for treating consecutive sequences as a single sequence.
Parameters
iterables...Array<Iterable<T>>
Returns Iterable<T>
Returns an iterator that counts up values starting with number start
(default 0), incrementing by step. To decrement, use a negative step
number.
Parameters
Returns Iterable<number>
Non-lazy version of icompress().
Parameters
dataIterable<T>selectorsIterable<boolean>
Returns Array<T>
Returns an iterator producing elements from the iterable and saving a copy of each. When the iterable is exhausted, return elements from the saved copy. Repeats indefinitely.
Parameters
iterableIterable<T>
Returns Iterable<T>
Returns an iterator that drops elements from the iterable as long as the predicate is true; afterwards, returns every remaining element. Note, the iterator does not produce any output until the predicate first becomes false.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterator that filters elements from data returning only those
that have a corresponding element in selectors that evaluates to true.
Stops when either the data or selectors iterables has been exhausted.
Parameters
dataIterable<T>selectorsIterable<boolean>
Returns Iterable<T>
Returns an iterator that filters elements from iterable returning only those for which the predicate is true.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterator that computes the given mapper function using arguments from each of the iterables.
Parameters
iterableIterable<T>mapperfunction (T): V
Returns Iterable<V>
Returns an iterator that returns selected elements from the iterable. If
start is non-zero, then elements from the iterable are skipped until start
is reached. Then, elements are returned by making steps of step (defaults
to 1). If set to higher than 1, items will be skipped. If stop is
provided, then iteration continues until the iterator reached that index,
otherwise, the iterable will be fully exhausted. islice() does not
support negative values for start, stop, or step.
Parameters
Returns Iterable<T>
Returns an iterator that aggregates elements from each of the iterables.
Used for lock-step iteration over several iterables at a time. When
iterating over two iterables, use izip2. When iterating over three
iterables, use izip3, etc. izip is an alias for izip2.
Parameters
xsIterable<T1>ysIterable<T2>
Returns Iterable<[T1, T2]>
Like izip2, but for three input iterables.
Parameters
xsIterable<T1>ysIterable<T2>zsIterable<T3>
Returns Iterable<[T1, T2, T3]>
Like the other izip's, but generalized. Due to type system limitations, you can only "generially" zip iterables with homogeneous types, so you cannot mix types like <A, B> like you can with izip2()
Parameters
iters...Array<Iterable<T>>
Returns Iterable<Array<T>>
Return successive r-length permutations of elements in the iterable.
If r is not specified, then r defaults to the length of the iterable and
all possible full-length permutations are generated.
Permutations are emitted in lexicographic sort order. So, if the input iterable is sorted, the permutation tuples will be produced in sorted order.
Elements are treated as unique based on their position, not on their value. So if the input elements are unique, there will be no repeat values in each permutation.
Parameters
iterableIterable<T>rMaybe<number>
Returns Iterable<Array<T>>
Returns an iterator that produces elements from the iterable as long as the predicate is true.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns true when all of the items in iterable are truthy. An optional key function can be used to define what truthiness means for this specific collection.
Examples:
all([]) // => true
all([0]) // => false
all([0, 1, 2]) // => false
all([1, 2, 3]) // => true
Examples with using a key function:
all([2, 4, 6], n => n % 2 === 0) // => true
all([2, 4, 5], n => n % 2 === 0) // => false
Parameters
iterableIterable<T>keyFnPredicate<T> (optional, defaultidentityPredicate)
Returns boolean
Returns true when any of the items in iterable are truthy. An optional key function can be used to define what truthiness means for this specific collection.
Examples:
any([]) // => false
any([0]) // => false
any([0, 1, null, undefined]) // => true
Examples with using a key function:
any([1, 4, 5], n => n % 2 === 0) // => true
any([{name: 'Bob'}, {name: 'Alice'}], person => person.name.startsWith('C')) // => false
Parameters
iterableIterable<T>keyFnPredicate<T> (optional, defaultidentityPredicate)
Returns boolean
Returns true when any of the items in the iterable are equal to the target object.
Examples:
contains([], 'whatever') // => false
contains([3], 42) // => false
contains([3], 3) // => true
contains([0, 1, 2], 2) // => true
Parameters
haystackIterable<T>needleT
Returns boolean
Returns an iterable of enumeration pairs. Iterable must be a sequence, an iterator, or some other object which supports iteration. The elements produced by returns a tuple containing a counter value (starting from 0 by default) and the values obtained from iterating over given iterable.
Example:
import { enumerate } from 'itertools';
console.log([...enumerate(['hello', 'world'])]);
// [0, 'hello'], [1, 'world']]
Parameters
iterableIterable<T>startnumber (optional, default0)
Returns Iterable<[number, T]>
Non-lazy version of ifilter().
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Array<T>
Returns an iterator object for the given iterable. This can be used to manually get an iterator for any iterable datastructure. The purpose and main use case of this function is to get a single iterator (a thing with state, think of it as a "cursor") which can only be consumed once.
Parameters
iterableIterable<T>
Returns Iterator<T>
Non-lazy version of imap().
Parameters
iterableIterable<T>mapperfunction (T): V
Returns Array<V>
Return the largest item in an iterable. Only works for numbers, as ordering
is pretty poorly defined on any other data type in JS. The optional keyFn
argument specifies a one-argument ordering function like that used for
sorted().
If the iterable is empty, undefined is returned.
If multiple items are maximal, the function returns either one of them, but which one is not defined.
Parameters
iterableIterable<T>keyFnfunction (T): number (optional, defaultnumberIdentity)
Returns Maybe<T>
Return the smallest item in an iterable. Only works for numbers, as
ordering is pretty poorly defined on any other data type in JS. The
optional keyFn argument specifies a one-argument ordering function like
that used for sorted().
If the iterable is empty, undefined is returned.
If multiple items are minimal, the function returns either one of them, but which one is not defined.
Parameters
iterableIterable<T>keyFnfunction (T): number (optional, defaultnumberIdentity)
Returns Maybe<T>
TODO
Parameters
Returns Iterable<number>
TODO: Reducer function with a start value.
Parameters
iterableIterable<T>reducerfunction (O, T, number): OstartO
Returns O
TODO: Document Reducer function without a start value. The start value will be the first item in the input iterable. For this reason, the function may not necessarily return anything (i.e. if the input is empty), and the inputs and the outputs must be of homogeneous types.
Parameters
iterableIterable<T>reducerfunction (T, T, number): T
Returns Maybe<T>
TODO
Parameters
iterableIterable<T>keyFnfunction (T): Primitive (optional, defaultprimitiveIdentity)reverseboolean (optional, defaultfalse)
Returns Array<T>
TODO
Parameters
iterableIterable<number>
Returns number
TODO
Parameters
xsIterable<T1>ysIterable<T2>
Returns Array<[T1, T2]>
TODO
Parameters
xsIterable<T1>ysIterable<T2>zsIterable<T3>
Returns Array<[T1, T2, T3]>
Returns an iterable containing only the first n elements of the given
iterable.
Parameters
nnumberiterableIterable<T>
Returns Iterable<T>
Non-lazy version of itake().
Parameters
nnumberiterableIterable<T>
Returns Array<T>
Returns an iterable containing only the first n elements of the given
iterable.
Parameters
nnumberiterableIterable<T>
Returns Iterable<T>
Non-lazy version of itake().
Parameters
nnumberiterableIterable<T>
Returns Array<T>
Returns true when all of the items in iterable are truthy. An optional key function can be used to define what truthiness means for this specific collection.
Examples:
all([]) // => true
all([0]) // => false
all([0, 1, 2]) // => false
all([1, 2, 3]) // => true
Examples with using a key function:
all([2, 4, 6], n => n % 2 === 0) // => true
all([2, 4, 5], n => n % 2 === 0) // => false
Parameters
iterableIterable<T>keyFnPredicate<T> (optional, defaultidentityPredicate)
Returns boolean
Returns true when any of the items in iterable are truthy. An optional key function can be used to define what truthiness means for this specific collection.
Examples:
any([]) // => false
any([0]) // => false
any([0, 1, null, undefined]) // => true
Examples with using a key function:
any([1, 4, 5], n => n % 2 === 0) // => true
any([{name: 'Bob'}, {name: 'Alice'}], person => person.name.startsWith('C')) // => false
Parameters
iterableIterable<T>keyFnPredicate<T> (optional, defaultidentityPredicate)
Returns boolean
Returns true when any of the items in the iterable are equal to the target object.
Examples:
contains([], 'whatever') // => false
contains([3], 42) // => false
contains([3], 3) // => true
contains([0, 1, 2], 2) // => true
Parameters
haystackIterable<T>needleT
Returns boolean
Returns an iterable of enumeration pairs. Iterable must be a sequence, an iterator, or some other object which supports iteration. The elements produced by returns a tuple containing a counter value (starting from 0 by default) and the values obtained from iterating over given iterable.
Example:
import { enumerate } from 'itertools';
console.log([...enumerate(['hello', 'world'])]);
// [0, 'hello'], [1, 'world']]
Parameters
iterableIterable<T>startnumber (optional, default0)
Returns Iterable<[number, T]>
Non-lazy version of ifilter().
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Array<T>
Returns an iterator object for the given iterable. This can be used to manually get an iterator for any iterable datastructure. The purpose and main use case of this function is to get a single iterator (a thing with state, think of it as a "cursor") which can only be consumed once.
Parameters
iterableIterable<T>
Returns Iterator<T>
Non-lazy version of imap().
Parameters
iterableIterable<T>mapperfunction (T): V
Returns Array<V>
Return the largest item in an iterable. Only works for numbers, as ordering
is pretty poorly defined on any other data type in JS. The optional keyFn
argument specifies a one-argument ordering function like that used for
sorted().
If the iterable is empty, undefined is returned.
If multiple items are maximal, the function returns either one of them, but which one is not defined.
Parameters
iterableIterable<T>keyFnfunction (T): number (optional, defaultnumberIdentity)
Returns Maybe<T>
Return the smallest item in an iterable. Only works for numbers, as
ordering is pretty poorly defined on any other data type in JS. The
optional keyFn argument specifies a one-argument ordering function like
that used for sorted().
If the iterable is empty, undefined is returned.
If multiple items are minimal, the function returns either one of them, but which one is not defined.
Parameters
iterableIterable<T>keyFnfunction (T): number (optional, defaultnumberIdentity)
Returns Maybe<T>
TODO
Parameters
Returns Iterable<number>
TODO: Reducer function with a start value.
Parameters
iterableIterable<T>reducerfunction (O, T, number): OstartO
Returns O
TODO: Document Reducer function without a start value. The start value will be the first item in the input iterable. For this reason, the function may not necessarily return anything (i.e. if the input is empty), and the inputs and the outputs must be of homogeneous types.
Parameters
iterableIterable<T>reducerfunction (T, T, number): T
Returns Maybe<T>
TODO
Parameters
iterableIterable<T>keyFnfunction (T): Primitive (optional, defaultprimitiveIdentity)reverseboolean (optional, defaultfalse)
Returns Array<T>
TODO
Parameters
iterableIterable<number>
Returns number
TODO
Parameters
xsIterable<T1>ysIterable<T2>
Returns Array<[T1, T2]>
TODO
Parameters
xsIterable<T1>ysIterable<T2>zsIterable<T3>
Returns Array<[T1, T2, T3]>
Returns an iterator that returns elements from the first iterable until it is exhausted, then proceeds to the next iterable, until all of the iterables are exhausted. Used for treating consecutive sequences as a single sequence.
Parameters
iterables...Array<Iterable<T>>
Returns Iterable<T>
Returns an iterator that counts up values starting with number start
(default 0), incrementing by step. To decrement, use a negative step
number.
Parameters
Returns Iterable<number>
Non-lazy version of icompress().
Parameters
dataIterable<T>selectorsIterable<boolean>
Returns Array<T>
Returns an iterator producing elements from the iterable and saving a copy of each. When the iterable is exhausted, return elements from the saved copy. Repeats indefinitely.
Parameters
iterableIterable<T>
Returns Iterable<T>
Returns an iterator that drops elements from the iterable as long as the predicate is true; afterwards, returns every remaining element. Note, the iterator does not produce any output until the predicate first becomes false.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterator that filters elements from data returning only those
that have a corresponding element in selectors that evaluates to true.
Stops when either the data or selectors iterables has been exhausted.
Parameters
dataIterable<T>selectorsIterable<boolean>
Returns Iterable<T>
Returns an iterator that filters elements from iterable returning only those for which the predicate is true.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterator that computes the given mapper function using arguments from each of the iterables.
Parameters
iterableIterable<T>mapperfunction (T): V
Returns Iterable<V>
Returns an iterator that returns selected elements from the iterable. If
start is non-zero, then elements from the iterable are skipped until start
is reached. Then, elements are returned by making steps of step (defaults
to 1). If set to higher than 1, items will be skipped. If stop is
provided, then iteration continues until the iterator reached that index,
otherwise, the iterable will be fully exhausted. islice() does not
support negative values for start, stop, or step.
Parameters
Returns Iterable<T>
Returns an iterator that aggregates elements from each of the iterables.
Used for lock-step iteration over several iterables at a time. When
iterating over two iterables, use izip2. When iterating over three
iterables, use izip3, etc. izip is an alias for izip2.
Parameters
xsIterable<T1>ysIterable<T2>
Returns Iterable<[T1, T2]>
Like izip2, but for three input iterables.
Parameters
xsIterable<T1>ysIterable<T2>zsIterable<T3>
Returns Iterable<[T1, T2, T3]>
Like the other izip's, but generalized. Due to type system limitations, you can only "generially" zip iterables with homogeneous types, so you cannot mix types like <A, B> like you can with izip2()
Parameters
iters...Array<Iterable<T>>
Returns Iterable<Array<T>>
Return successive r-length permutations of elements in the iterable.
If r is not specified, then r defaults to the length of the iterable and
all possible full-length permutations are generated.
Permutations are emitted in lexicographic sort order. So, if the input iterable is sorted, the permutation tuples will be produced in sorted order.
Elements are treated as unique based on their position, not on their value. So if the input elements are unique, there will be no repeat values in each permutation.
Parameters
iterableIterable<T>rMaybe<number>
Returns Iterable<Array<T>>
Returns an iterator that produces elements from the iterable as long as the predicate is true.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Removes all undefined values from the given object. Returns a new object.
Examples: compactObject({ a: 1, b: undefined, c: 0 }) // ==> { a: 1, c: 0 }
Parameters
objO
Returns $ObjMap<O, function (Maybe<T>): T>
Returns 0 or more values for every value in the given iterable
Examples:
Get Ids for an Author and its aliases
flatmap(author => [author.id, ...author.aliases.map(a => a.id)], authors)
Parameters
iterableIterable<T>mapperfunction (T): Iterable<S>
Returns Iterable<S>
Returns an iterator that returns elements from the first iterable until it is exhausted, then proceeds to the next iterable, until all of the iterables are exhausted. Used for treating consecutive sequences as a single sequence.
Parameters
iterables...Array<Iterable<T>>
Returns Iterable<T>
Returns an iterator that counts up values starting with number start
(default 0), incrementing by step. To decrement, use a negative step
number.
Parameters
Returns Iterable<number>
Non-lazy version of icompress().
Parameters
dataIterable<T>selectorsIterable<boolean>
Returns Array<T>
Returns an iterator producing elements from the iterable and saving a copy of each. When the iterable is exhausted, return elements from the saved copy. Repeats indefinitely.
Parameters
iterableIterable<T>
Returns Iterable<T>
Returns an iterator that drops elements from the iterable as long as the predicate is true; afterwards, returns every remaining element. Note, the iterator does not produce any output until the predicate first becomes false.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterator that filters elements from data returning only those
that have a corresponding element in selectors that evaluates to true.
Stops when either the data or selectors iterables has been exhausted.
Parameters
dataIterable<T>selectorsIterable<boolean>
Returns Iterable<T>
Returns an iterator that filters elements from iterable returning only those for which the predicate is true.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterator that computes the given mapper function using arguments from each of the iterables.
Parameters
iterableIterable<T>mapperfunction (T): V
Returns Iterable<V>
Returns an iterator that returns selected elements from the iterable. If
start is non-zero, then elements from the iterable are skipped until start
is reached. Then, elements are returned by making steps of step (defaults
to 1). If set to higher than 1, items will be skipped. If stop is
provided, then iteration continues until the iterator reached that index,
otherwise, the iterable will be fully exhausted. islice() does not
support negative values for start, stop, or step.
Parameters
Returns Iterable<T>
Returns an iterator that aggregates elements from each of the iterables.
Used for lock-step iteration over several iterables at a time. When
iterating over two iterables, use izip2. When iterating over three
iterables, use izip3, etc. izip is an alias for izip2.
Parameters
xsIterable<T1>ysIterable<T2>
Returns Iterable<[T1, T2]>
Like izip2, but for three input iterables.
Parameters
xsIterable<T1>ysIterable<T2>zsIterable<T3>
Returns Iterable<[T1, T2, T3]>
Like the other izip's, but generalized. Due to type system limitations, you can only "generially" zip iterables with homogeneous types, so you cannot mix types like <A, B> like you can with izip2()
Parameters
iters...Array<Iterable<T>>
Returns Iterable<Array<T>>
Return successive r-length permutations of elements in the iterable.
If r is not specified, then r defaults to the length of the iterable and
all possible full-length permutations are generated.
Permutations are emitted in lexicographic sort order. So, if the input iterable is sorted, the permutation tuples will be produced in sorted order.
Elements are treated as unique based on their position, not on their value. So if the input elements are unique, there will be no repeat values in each permutation.
Parameters
iterableIterable<T>rMaybe<number>
Returns Iterable<Array<T>>
Returns an iterator that produces elements from the iterable as long as the predicate is true.
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Iterable<T>
Returns an iterable containing only the first n elements of the given
iterable.
Parameters
nnumberiterableIterable<T>
Returns Iterable<T>
Non-lazy version of itake().
Parameters
nnumberiterableIterable<T>
Returns Array<T>
Returns true when all of the items in iterable are truthy. An optional key function can be used to define what truthiness means for this specific collection.
Examples:
all([]) // => true
all([0]) // => false
all([0, 1, 2]) // => false
all([1, 2, 3]) // => true
Examples with using a key function:
all([2, 4, 6], n => n % 2 === 0) // => true
all([2, 4, 5], n => n % 2 === 0) // => false
Parameters
iterableIterable<T>keyFnPredicate<T> (optional, defaultidentityPredicate)
Returns boolean
Returns true when any of the items in iterable are truthy. An optional key function can be used to define what truthiness means for this specific collection.
Examples:
any([]) // => false
any([0]) // => false
any([0, 1, null, undefined]) // => true
Examples with using a key function:
any([1, 4, 5], n => n % 2 === 0) // => true
any([{name: 'Bob'}, {name: 'Alice'}], person => person.name.startsWith('C')) // => false
Parameters
iterableIterable<T>keyFnPredicate<T> (optional, defaultidentityPredicate)
Returns boolean
Returns true when any of the items in the iterable are equal to the target object.
Examples:
contains([], 'whatever') // => false
contains([3], 42) // => false
contains([3], 3) // => true
contains([0, 1, 2], 2) // => true
Parameters
haystackIterable<T>needleT
Returns boolean
Returns an iterable of enumeration pairs. Iterable must be a sequence, an iterator, or some other object which supports iteration. The elements produced by returns a tuple containing a counter value (starting from 0 by default) and the values obtained from iterating over given iterable.
Example:
import { enumerate } from 'itertools';
console.log([...enumerate(['hello', 'world'])]);
// [0, 'hello'], [1, 'world']]
Parameters
iterableIterable<T>startnumber (optional, default0)
Returns Iterable<[number, T]>
Non-lazy version of ifilter().
Parameters
iterableIterable<T>predicatePredicate<T>
Returns Array<T>
Returns an iterator object for the given iterable. This can be used to manually get an iterator for any iterable datastructure. The purpose and main use case of this function is to get a single iterator (a thing with state, think of it as a "cursor") which can only be consumed once.
Parameters
iterableIterable<T>
Returns Iterator<T>
Non-lazy version of imap().
Parameters
iterableIterable<T>mapperfunction (T): V
Returns Array<V>
Return the largest item in an iterable. Only works for numbers, as ordering
is pretty poorly defined on any other data type in JS. The optional keyFn
argument specifies a one-argument ordering function like that used for
sorted().
If the iterable is empty, undefined is returned.
If multiple items are maximal, the function returns either one of them, but which one is not defined.
Parameters
iterableIterable<T>keyFnfunction (T): number (optional, defaultnumberIdentity)
Returns Maybe<T>
Return the smallest item in an iterable. Only works for numbers, as
ordering is pretty poorly defined on any other data type in JS. The
optional keyFn argument specifies a one-argument ordering function like
that used for sorted().
If the iterable is empty, undefined is returned.
If multiple items are minimal, the function returns either one of them, but which one is not defined.
Parameters
iterableIterable<T>keyFnfunction (T): number (optional, defaultnumberIdentity)
Returns Maybe<T>
TODO
Parameters
Returns Iterable<number>
TODO: Reducer function with a start value.
Parameters
iterableIterable<T>reducerfunction (O, T, number): OstartO
Returns O
TODO: Document Reducer function without a start value. The start value will be the first item in the input iterable. For this reason, the function may not necessarily return anything (i.e. if the input is empty), and the inputs and the outputs must be of homogeneous types.
Parameters
iterableIterable<T>reducerfunction (T, T, number): T
Returns Maybe<T>
TODO
Parameters
iterableIterable<T>keyFnfunction (T): Primitive (optional, defaultprimitiveIdentity)reverseboolean (optional, defaultfalse)
Returns Array<T>
TODO
Parameters
iterableIterable<number>
Returns number
TODO
Parameters
xsIterable<T1>ysIterable<T2>
Returns Array<[T1, T2]>
TODO
Parameters
xsIterable<T1>ysIterable<T2>zsIterable<T3>
Returns Array<[T1, T2, T3]>