An iterator / async-iterator library with support for old platforms that don't have iterables or async-iterables. Iterly provides several useful functions for composing, manipulating and iterating through iterables, async-iterables, arrays, streams, and array-like objects such as nodejs Buffer.
Even though iterly doesn't use async functions or generators, and should work on browsers as far back as ie10, you will still need to pass your code through Babel or similar to transpile modern syntax used in this library, such as destructuring.
yarn add iterly or npm install iterly
- Iteration helpers
- Function composition
- Sync operators
- Async operators
- Sync / Async operators
- Range
- range
Loops over any iterable, async-iterable, iterator, async-iterator or array-like, calling fn for each item. If looping over an async-iterable / async-iterator a promise will be returned by each with the value of the final return from fn.
xnumber The number of async items to run in parallel, has no effect on sync iterables. (optional, default1)fn(function (value) | function (value, done)) The fn to call for each item. The function will be called for every value in the iterable / async-iterable. If the function has a second param (done) then the loop function will be called when the iterable / async-iterable is done, with a done value of true. If no second param (done) is provided then the loop function will only be called with the values from the iterable / async-iterable.it(iterable | asyncIterable) The iterable, async-iterable, iterator, async-iterator or array-like to loop over.
each((value) => console.log(value), [1, 2, 3, 4])
// Will print:
// 1
// 2
// 3
// 4Returns (Promise | undefined) Returns a Promise that resolves to the last value returned by fn if looping over an async-iterable. If looping over an iterable returns undefined.
Gets an iterator / async-iterator for any iterable, async-iterable, array-like, or function with a sentinel.
objObject The possible iterable to create an iterator for.optionsObject (optional, default{})options.sentinelAny distinct value to use as a stop indicator when creating an iterator from a function, see iterFn.options.isAsyncBoolean If true and obj is a function, an async-iterator will be returned. (optional, defaultfalse)
Returns (@@iterator | @@asyncIterator | undefined) Returns an iterator, async-iterator, or undefined if obj is not iterable.
Gets an iterator for any array-like; that is anything with a length property that can be indexed with array[index] notation.
a(Array | arrayLike) The array-like to create an iterator from.chunkSizenumber If set larger than zero, will break the array up into chunks of length chunkSize. (optional, default0)
var it = iterArray([1, 2, 3, 4])
// Will give you an iterator with the values: 1, 2, 3, 4
var it = iterArray([1, 2, 3, 4], 2)
// Will give you an iterator with the values: [1, 2], [3, 4]Returns @@iterator Returns an iterator with the values from the array-like.
Gets an iterator of [key, value] pairs for any javascript object.
oObject The object to create an iterator from. Only iterates over an objects own-properties.
var it = iterObject({a: 1, b: 2, c: 3})
// Will give you an iterator with the values: [a, 1], [b, 2], [c, 3]Returns @@iterator Returns an iterator with the [key, value] pairs from the object.
Turns a function into an iterator.
fnfunction ({i, sentinel}) The iterator will return whatever this function returns, until it returns the sentinel value, then it will stop. The function is given an object with an index i and the sentinel value, you can add any other state you want to keep between iterations to this object if you like.optionsObject This options object must contain the sentinel property, the sentinel is returned by fn to signal the end of iteration.options.sentinelAny distinct value to use as an indicator that the iterator function is done.options.isAsyncBoolean If true an async-iterator will be returned. (optional, defaultfalse)
var it = iterFn(({i, sentinel}) => i >= 4 ? sentinel : i * 2, {sentinel: {}})
// Will give you an iterator with the values: 0, 2, 4, 6Returns (@@iterator | @@asyncIterator) Returns an iterator or async-iterator with the values returned by fn.
Perhaps the most useful function here; allows you to compose (combine) other functions into one new function that takes one argument of an iterable, async-iterable, iterator, or async-iterator.
fns...function Any number of functions to combine.
var urlPrefix = 'http://some.resource.com/'
var files = ['file.txt', 'file2.txt', 'file3.txt', 'file4.txt']
var getShortTexts = compose(
filter.curry(file => file != 'file3.txt'), // Removes file3.txt
map.curry(file => urlPrefix + file), // Adds the url prefix to the file names, creating the file url
amap.curry(url => fetch(url).then(res => res.text())), // Fetches the files from the web
afilter.curry(txt => txt.length <= 140), // Removes files longer than 140 characters
)
each(txt => console.log(txt), getShortTexts([files]))
// Will print out the contents of the files with 140 or fewer chracters, skipping file3.txt.Returns function (it: anyIterableOrAsyncIterable) The composed function.
Returns a curried version of the provided function.
fnfunction The function to curry.args...any? Any arguments to bind.
Returns function Returns the curried function.
A function that maps iterator or iterable values over a function.
fnfunction (value: any, index: number) The function to modify each value in the iterator.it@@iterator The iterator or iterable to map over.
var it = map(v => 2 * v, [1, 2, 3, 4])
// Will give you an iterator with the values: 2, 4, 6, 8Returns @@iterator Returns an iterator with values that will be updated by fn.
Allows you to curry the arguments, most useful when used with compose.
args...any The arguments to bind.
var curried = map.curry(v => 2 * v)
var it = [1, 2, 3, 4]
it = curried(it)
// Will give you an iterator with the values: 2, 4, 6, 8Returns curriedFunction The curried version of the original function, with bindable args.
A function that reduces all the items in an iterator or iterable to one value.
fnfunction (accumulator: any, value: any, index: number) The reducer function continually updates the accumulator, until the iterator ends, then the accumulated value is returned.accThe accumulator's initial value, each item in the iterator or iterable will be added to this by fn.it@@iterator The iterator or iterable to reduce.
var it = reduce((acc, v) => acc += v, 0, [1, 2, 3, 4])
// Will give you an iterator with the value: 10
var it = reduce((acc, v, i) => (acc[i] = v, acc), [], [1, 2, 3, 4])
// Will give you an iterator with a single item, which will be an array: [1, 2, 3, 4]Returns @@iterator Returns an iterator with only one value.
Allows you to curry the arguments, most useful when used with compose.
args...any The arguments to bind.
var curried = reduce.curry((acc, val) => acc + val)
var it = [1, 2, 3, 4]
it = curried(it)
// Will give you an iterator with the value: 10Returns curriedFunction The curried version of the original function, with bindable args.
A function that keeps values in an iterator or iterable only if fn returns true.
fnfunction (value: any, index: number) The test function to filter items, return true to keep the item, false to remove it.it@@iterator The iterator or iterable to filter.
var it = filter(v => v != 2, [1, 2, 3, 4])
// Will give you an iterator with the values: 1, 3, 4Returns @@iterator Returns an iterator with only the values that passed the test fn.
Allows you to curry the arguments, most useful when used with compose.
args...any The arguments to bind.
var curried = filter.curry(v => v != 2)
var it = [1, 2, 3, 4]
it = curried(it)
// Will give you an iterator with the values: 1, 3, 4Returns curriedFunction The curried version of the original function, with bindable args.
A function that maps iterator, iterable, async-iterator or async-iterable values over a function.
fnfunction (value: any, index: number) The function to modify each value in the iterator.it(@@iterator | @@asyncIterator) The iterator, iterable, async-iterator or async-iterable to map over.
var it = amap(v => 2 * v, [1, 2, 3, 4])
// Will give you an async-iterator with the promised values: 2, 4, 6, 8
var urls = ['http://some.resource.com/file.txt', 'http://some.resource.com/file2.txt']
var it = amap(url => fetch(url).then(res => res.text()), urls)
it = amap(txt => txt.slice(0, 140), it)
each(txt => console.log(txt), it)
// Will print the first 140 characters of text for each file referenced by the urlsReturns @@asyncIterator Returns an async-iterator with values returned by fn.
Allows you to curry the arguments, most useful when used with compose.
args...any The arguments to bind.
var curried = amap.curry(v => 2 * v)
var it = [1, 2, 3, 4]
it = curried(it)
// Will give you an async-iterator with the promised values: 2, 4, 6, 8Returns curriedFunction The curried version of the original function, with bindable args.
A function that reduces an iterator, iterable, async-iterator or async-iterable to one promised value.
nnumber If a value greater than 0 is provided, then areduce will create multiple, grouped reductions, each made ofnitems, like a scan fn. (optional, default0)fnfunction (accumulator: any, value: any, index: number) The reducer function continually updates the accumulator, until the iterator / async-iterator ends, then the accumulated value is returned.accThe accumulator's initial value, each item in the iterator or iterable will be added to this by fn.it(@@iterator | @@asyncIterator) The iterator, iterable, async-iterator or async-iterable to reduce.
var it = areduce((acc, v) => acc += v, 0, [1, 2, 3, 4])
// Will give you an async-iterator with the promised value: 10
var urls = ['http://some.resource.com/file.txt', 'http://some.resource.com/file2.txt']
var it = amap(url => fetch(url).then(res => res.text()), urls)
it = areduce((acc, txt) => acc + txt.slice(0, 140), '', it)
each(txt => console.log(txt), it)
// Will print the combined 280 characters of text from each file referenced by the urlsReturns @@asyncIterator Returns an async-iterator with only one promised value.
Allows you to curry the arguments, most useful when used with compose.
args...any The arguments to bind.
var curried = areduce.curry((acc, val) => acc + val)
var it = [1, 2, 3, 4]
it = curried(it)
// Will give you an async-iterator with the promised value: 10Returns curriedFunction The curried version of the original function, with bindable args.
A function that keeps values in an iterator, iterable, async-iterator or async-iterable, only if fn returns true.
fnfunction (value: any, index: number) The test function to filter items, return true to keep the item, false to remove it.it(@@iterator | @@asyncIterator) The iterator, iterable, async-iterator or async-iterable to filter.
var it = afilter(v => v != 2, [1, 2, 3, 4])
// Will give you an async-iterator with the promised values: 1, 3, 4
var urls = ['http://some.resource.com/file.txt', 'http://some.resource.com/file2.txt']
var it = amap(url => fetch(url).then(res => res.text()), urls)
it = afilter(txt => txt.length < 140, it)
each(txt => console.log(txt), it)
// Will only print the text of the files, referenced by the urls, with fewer than 140 charactersReturns @@asyncIterator Returns an async-iterator with the values that passed the test fn.
Allows you to curry the arguments, most useful when used with compose.
args...any The arguments to bind.
var curried = afilter.curry(v => v != 2)
var it = [1, 2, 3, 4]
it = curried(it)
// Will give you an async-iterator with the promised values: 1, 3, 4Returns curriedFunction The curried version of the original function, with bindable args.
Enumerate takes an iterable, async-iterable, iterator, or async-iterator and returns the same with its values updated with an [index, value] pair, starting at 0 or at the optional start arg.
startnumber The optional index start. (optional, default0)it(iterable | asyncIterable) The iterable or async-iterable to return.
var arr = ['a', 'b', 'c', 'd']
var it = enumerate(arr)
// Will give you an iterator with the values: [0, 'a'], [1, 'b'], [2, 'c'], [3, 'd']Returns (iterator | asyncIterator) Returns an iterator or async-iterator with the [index, value] pair items.
Creates a Range object that can be iterated over.
startnumber The start of the range (inclusive). (optional, default0)stopnumber The end of the range (exclusive).stepnumber The stride of the range. (optional, default1)
Returns Range
Creates an iterator of all the values in the range.
Returns Iterator
Creates an iterator of all the values in the range.
Returns Iterator
Creates an iterator of all the entries in the range.
Returns Iterator Returns value pairs [value, value], like Set.
Get an item from a range by index.
idxnumber The index of the value in the range.
Returns number Returns the value at the index, or undefined.
Check if a value exists in a range.
valnumber The value to look for.
Returns boolean Returns true if the value exists.
Find the index of a value in the range.
valnumber The value to look for.
Returns number Returns the index if the value exists, -1 otherwise.
An alternative, static method, Range constructor.
startnumber The start of the range (inclusive). (optional, default0)stopnumber The end of the range (exclusive).stepnumber The stride of the range. (optional, default1)
Returns Range
An alternative, functional, Range constructor.
startnumber The start of the range (inclusive). (optional, default0)stopnumber The end of the range (exclusive).stepnumber The stride of the range. (optional, default1)
Returns Range