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/**
* Copyright (c) 2016, Lee Byron
* All rights reserved.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @ignore
*/
/**
* [Iterator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#iterator)
* is a *protocol* which describes a standard way to produce a sequence of
* values, typically the values of the Iterable represented by this Iterator.
*
* While described by the [ES2015 version of JavaScript](http://www.ecma-international.org/ecma-262/6.0/#sec-iterator-interface)
* it can be utilized by any version of JavaScript.
*
* @typedef {Object} Iterator
* @template T The type of each iterated value
* @property {function (): { value: T, done: boolean }} next
* A method which produces either the next value in a sequence or a result
* where the `done` property is `true` indicating the end of the Iterator.
*/
/**
* [Iterable](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#iterable)
* is a *protocol* which when implemented allows a JavaScript object to define
* their iteration behavior, such as what values are looped over in a `for..of`
* loop or `iterall`'s `forEach` function. Many [built-in types](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#Builtin_iterables)
* implement the Iterable protocol, including `Array` and `Map`.
*
* While described by the [ES2015 version of JavaScript](http://www.ecma-international.org/ecma-262/6.0/#sec-iterable-interface)
* it can be utilized by any version of JavaScript.
*
* @typedef {Object} Iterable
* @template T The type of each iterated value
* @property {function (): Iterator} Symbol.iterator
* A method which produces an Iterator for this Iterable.
*/
// In ES2015 (or a polyfilled) environment, this will be Symbol.iterator
var SYMBOL_ITERATOR = typeof Symbol === 'function' && Symbol.iterator
/**
* A property name to be used as the name of an Iterable's method responsible
* for producing an Iterator, referred to as `@@iterator`. Typically represents
* the value `Symbol.iterator` but falls back to the string `"@@iterator"` when
* `Symbol.iterator` is not defined.
*
* Use `$$iterator` for defining new Iterables instead of `Symbol.iterator`,
* but do not use it for accessing existing Iterables, instead use
* `getIterator()` or `isIterable()`.
*
* @example
*
* var $$iterator = require('iterall').$$iterator
*
* function Counter (to) {
* this.to = to
* }
*
* Counter.prototype[$$iterator] = function () {
* return {
* to: this.to,
* num: 0,
* next () {
* if (this.num >= this.to) {
* return { value: undefined, done: true }
* }
* return { value: this.num++, done: false }
* }
* }
* }
*
* var counter = new Counter(3)
* for (var number of counter) {
* console.log(number) // 0 ... 1 ... 2
* }
*
* @type {Symbol|string}
*/
var $$iterator = SYMBOL_ITERATOR || '@@iterator'
exports.$$iterator = $$iterator
/**
* Returns true if the provided object implements the Iterator protocol via
* either implementing a `Symbol.iterator` or `"@@iterator"` method.
*
* @example
*
* var isIterable = require('iterall').isIterable
* isIterable([ 1, 2, 3 ]) // true
* isIterable('ABC') // true
* isIterable({ length: 1, 0: 'Alpha' }) // false
* isIterable({ key: 'value' }) // false
* isIterable(new Map()) // true
*
* @param obj
* A value which might implement the Iterable protocol.
* @return {boolean} true if Iterable.
*/
function isIterable(obj) {
return !!getIteratorMethod(obj)
}
exports.isIterable = isIterable
/**
* Returns true if the provided object implements the Array-like protocol via
* defining a positive-integer `length` property.
*
* @example
*
* var isArrayLike = require('iterall').isArrayLike
* isArrayLike([ 1, 2, 3 ]) // true
* isArrayLike('ABC') // true
* isArrayLike({ length: 1, 0: 'Alpha' }) // true
* isArrayLike({ key: 'value' }) // false
* isArrayLike(new Map()) // false
*
* @param obj
* A value which might implement the Array-like protocol.
* @return {boolean} true if Array-like.
*/
function isArrayLike(obj) {
var length = obj != null && obj.length
return typeof length === 'number' && length >= 0 && length % 1 === 0
}
exports.isArrayLike = isArrayLike
/**
* Returns true if the provided object is an Object (i.e. not a string literal)
* and is either Iterable or Array-like.
*
* This may be used in place of [Array.isArray()][isArray] to determine if an
* object should be iterated-over. It always excludes string literals and
* includes Arrays (regardless of if it is Iterable). It also includes other
* Array-like objects such as NodeList, TypedArray, and Buffer.
*
* @example
*
* var isCollection = require('iterall').isCollection
* isCollection([ 1, 2, 3 ]) // true
* isCollection('ABC') // false
* isCollection({ length: 1, 0: 'Alpha' }) // true
* isCollection({ key: 'value' }) // false
* isCollection(new Map()) // true
*
* @example
*
* var forEach = require('iterall').forEach
* if (isCollection(obj)) {
* forEach(obj, function (value) {
* console.log(value)
* })
* }
*
* @param obj
* An Object value which might implement the Iterable or Array-like protocols.
* @return {boolean} true if Iterable or Array-like Object.
*/
function isCollection(obj) {
return Object(obj) === obj && (isArrayLike(obj) || isIterable(obj))
}
exports.isCollection = isCollection
/**
* If the provided object implements the Iterator protocol, its Iterator object
* is returned. Otherwise returns undefined.
*
* @example
*
* var getIterator = require('iterall').getIterator
* var iterator = getIterator([ 1, 2, 3 ])
* iterator.next() // { value: 1, done: false }
* iterator.next() // { value: 2, done: false }
* iterator.next() // { value: 3, done: false }
* iterator.next() // { value: undefined, done: true }
*
* @template T the type of each iterated value
* @param {Iterable} iterable
* An Iterable object which is the source of an Iterator.
* @return {Iterator} new Iterator instance.
*/
function getIterator(iterable) {
var method = getIteratorMethod(iterable)
if (method) {
return method.call(iterable)
}
}
exports.getIterator = getIterator
/**
* If the provided object implements the Iterator protocol, the method
* responsible for producing its Iterator object is returned.
*
* This is used in rare cases for performance tuning. This method must be called
* with obj as the contextual this-argument.
*
* @example
*
* var getIteratorMethod = require('iterall').getIteratorMethod
* var myArray = [ 1, 2, 3 ]
* var method = getIteratorMethod(myArray)
* if (method) {
* var iterator = method.call(myArray)
* }
*
* @template T the type of each iterated value
* @param {Iterable} iterable
* An Iterable object which defines an `@@iterator` method.
* @return {function(): Iterator} `@@iterator` method.
*/
function getIteratorMethod(iterable) {
if (iterable != null) {
var method =
(SYMBOL_ITERATOR && iterable[SYMBOL_ITERATOR]) || iterable['@@iterator']
if (typeof method === 'function') {
return method
}
}
}
exports.getIteratorMethod = getIteratorMethod
/**
* Similar to `getIterator()`, this method returns a new Iterator given an
* Iterable. However it will also create an Iterator for a non-Iterable
* Array-like collection, such as Array in a non-ES2015 environment.
*
* `createIterator` is complimentary to `forEach`, but allows a "pull"-based
* iteration as opposed to `forEach`'s "push"-based iteration.
*
* `createIterator` produces an Iterator for Array-likes with the same behavior
* as ArrayIteratorPrototype described in the ECMAScript specification, and
* does *not* skip over "holes".
*
* @example
*
* var createIterator = require('iterall').createIterator
*
* var myArraylike = { length: 3, 0: 'Alpha', 1: 'Bravo', 2: 'Charlie' }
* var iterator = createIterator(myArraylike)
* iterator.next() // { value: 'Alpha', done: false }
* iterator.next() // { value: 'Bravo', done: false }
* iterator.next() // { value: 'Charlie', done: false }
* iterator.next() // { value: undefined, done: true }
*
* @template T the type of each iterated value
* @param {Iterable|{ length: number }} collection
* An Iterable or Array-like object to produce an Iterator.
* @return {Iterator} new Iterator instance.
*/
function createIterator(collection) {
if (collection != null) {
var iterator = getIterator(collection)
if (iterator) {
return iterator
}
if (isArrayLike(collection)) {
return new ArrayLikeIterator(collection)
}
}
}
exports.createIterator = createIterator
// When the object provided to `createIterator` is not Iterable but is
// Array-like, this simple Iterator is created.
function ArrayLikeIterator(obj) {
this._o = obj
this._i = 0
}
// Note: all Iterators are themselves Iterable.
ArrayLikeIterator.prototype[$$iterator] = function() {
return this
}
// A simple state-machine determines the IteratorResult returned, yielding
// each value in the Array-like object in order of their indicies.
ArrayLikeIterator.prototype.next = function() {
if (this._o === void 0 || this._i >= this._o.length) {
this._o = void 0
return { value: void 0, done: true }
}
return { value: this._o[this._i++], done: false }
}
/**
* Given an object which either implements the Iterable protocol or is
* Array-like, iterate over it, calling the `callback` at each iteration.
*
* Use `forEach` where you would expect to use a `for ... of` loop in ES6.
* However `forEach` adheres to the behavior of [Array#forEach][] described in
* the ECMAScript specification, skipping over "holes" in Array-likes. It will
* also delegate to a `forEach` method on `collection` if one is defined,
* ensuring native performance for `Arrays`.
*
* Similar to [Array#forEach][], the `callback` function accepts three
* arguments, and is provided with `thisArg` as the calling context.
*
* Note: providing an infinite Iterator to forEach will produce an error.
*
* [Array#forEach]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach
*
* @example
*
* var forEach = require('iterall').forEach
*
* forEach(myIterable, function (value, index, iterable) {
* console.log(value, index, iterable === myIterable)
* })
*
* @example
*
* // ES6:
* for (let value of myIterable) {
* console.log(value)
* }
*
* // Any JavaScript environment:
* forEach(myIterable, function (value) {
* console.log(value)
* })
*
* @template T the type of each iterated value
* @param {Iterable|{ length: number }} collection
* The Iterable or array to iterate over.
* @param {function(T, number, object)} callback
* Function to execute for each iteration, taking up to three arguments
* @param [thisArg]
* Optional. Value to use as `this` when executing `callback`.
*/
function forEach(collection, callback, thisArg) {
if (collection != null) {
if (typeof collection.forEach === 'function') {
return collection.forEach(callback, thisArg)
}
var i = 0
var iterator = getIterator(collection)
if (iterator) {
var step
while (!(step = iterator.next()).done) {
callback.call(thisArg, step.value, i++, collection)
// Infinite Iterators could cause forEach to run forever.
// After a very large number of iterations, produce an error.
/* istanbul ignore if */
if (i > 9999999) {
throw new TypeError('Near-infinite iteration.')
}
}
} else if (isArrayLike(collection)) {
for (; i < collection.length; i++) {
if (collection.hasOwnProperty(i)) {
callback.call(thisArg, collection[i], i, collection)
}
}
}
}
}
exports.forEach = forEach
/////////////////////////////////////////////////////
// //
// ASYNC ITERATORS //
// //
/////////////////////////////////////////////////////
/**
* [AsyncIterator](https://tc39.github.io/proposal-async-iteration/)
* is a *protocol* which describes a standard way to produce and consume an
* asynchronous sequence of values, typically the values of the AsyncIterable
* represented by this AsyncIterator.
*
* AsyncIterator is similar to Observable or Stream.
*
* While described as a proposed addition to the [ES2017 version of JavaScript](https://tc39.github.io/proposal-async-iteration/)
* it can be utilized by any version of JavaScript.
*
* @typedef {Object} AsyncIterator
* @template T The type of each iterated value
* @property {function (): Promise<{ value: T, done: boolean }>} next
* A method which produces a Promise which resolves to either the next value
* in a sequence or a result where the `done` property is `true` indicating
* the end of the sequence of values. It may also produce a Promise which
* becomes rejected, indicating a failure.
*/
/**
* AsyncIterable is a *protocol* which when implemented allows a JavaScript
* object to define their asynchronous iteration behavior, such as what values
* are looped over in a `for-await-of` loop or `iterall`'s `forAwaitEach`
* function.
*
* While described as a proposed addition to the [ES2017 version of JavaScript](https://tc39.github.io/proposal-async-iteration/)
* it can be utilized by any version of JavaScript.
*
* @typedef {Object} AsyncIterable
* @template T The type of each iterated value
* @property {function (): AsyncIterator} Symbol.asyncIterator
* A method which produces an AsyncIterator for this AsyncIterable.
*/
// In ES2017 (or a polyfilled) environment, this will be Symbol.asyncIterator
var SYMBOL_ASYNC_ITERATOR = typeof Symbol === 'function' && Symbol.asyncIterator
/**
* A property name to be used as the name of an AsyncIterable's method
* responsible for producing an Iterator, referred to as `@@asyncIterator`.
* Typically represents the value `Symbol.asyncIterator` but falls back to the
* string `"@@asyncIterator"` when `Symbol.asyncIterator` is not defined.
*
* Use `$$asyncIterator` for defining new AsyncIterables instead of
* `Symbol.asyncIterator`, but do not use it for accessing existing Iterables,
* instead use `getAsyncIterator()` or `isAsyncIterable()`.
*
* @example
*
* var $$asyncIterator = require('iterall').$$asyncIterator
*
* function Chirper (to) {
* this.to = to
* }
*
* Chirper.prototype[$$asyncIterator] = function () {
* return {
* to: this.to,
* num: 0,
* next () {
* return new Promise(function (resolve) {
* if (this.num >= this.to) {
* resolve({ value: undefined, done: true })
* } else {
* setTimeout(function () {
* resolve({ value: this.num++, done: false })
* }, 1000)
* }
* }
* }
* }
* }
*
* var chirper = new Chirper(3)
* for await (var number of chirper) {
* console.log(number) // 0 ...wait... 1 ...wait... 2
* }
*
* @type {Symbol|string}
*/
var $$asyncIterator = SYMBOL_ASYNC_ITERATOR || '@@asyncIterator'
exports.$$asyncIterator = $$asyncIterator
/**
* Returns true if the provided object implements the AsyncIterator protocol via
* either implementing a `Symbol.asyncIterator` or `"@@asyncIterator"` method.
*
* @example
*
* var isAsyncIterable = require('iterall').isAsyncIterable
* isAsyncIterable(myStream) // true
* isAsyncIterable('ABC') // false
*
* @param obj
* A value which might implement the AsyncIterable protocol.
* @return {boolean} true if AsyncIterable.
*/
function isAsyncIterable(obj) {
return !!getAsyncIteratorMethod(obj)
}
exports.isAsyncIterable = isAsyncIterable
/**
* If the provided object implements the AsyncIterator protocol, its
* AsyncIterator object is returned. Otherwise returns undefined.
*
* @example
*
* var getAsyncIterator = require('iterall').getAsyncIterator
* var asyncIterator = getAsyncIterator(myStream)
* asyncIterator.next().then(console.log) // { value: 1, done: false }
* asyncIterator.next().then(console.log) // { value: 2, done: false }
* asyncIterator.next().then(console.log) // { value: 3, done: false }
* asyncIterator.next().then(console.log) // { value: undefined, done: true }
*
* @template T the type of each iterated value
* @param {AsyncIterable} asyncIterable
* An AsyncIterable object which is the source of an AsyncIterator.
* @return {AsyncIterator} new AsyncIterator instance.
*/
function getAsyncIterator(asyncIterable) {
var method = getAsyncIteratorMethod(asyncIterable)
if (method) {
return method.call(asyncIterable)
}
}
exports.getAsyncIterator = getAsyncIterator
/**
* If the provided object implements the AsyncIterator protocol, the method
* responsible for producing its AsyncIterator object is returned.
*
* This is used in rare cases for performance tuning. This method must be called
* with obj as the contextual this-argument.
*
* @example
*
* var getAsyncIteratorMethod = require('iterall').getAsyncIteratorMethod
* var method = getAsyncIteratorMethod(myStream)
* if (method) {
* var asyncIterator = method.call(myStream)
* }
*
* @template T the type of each iterated value
* @param {AsyncIterable} asyncIterable
* An AsyncIterable object which defines an `@@asyncIterator` method.
* @return {function(): AsyncIterator} `@@asyncIterator` method.
*/
function getAsyncIteratorMethod(asyncIterable) {
if (asyncIterable != null) {
var method =
(SYMBOL_ASYNC_ITERATOR && asyncIterable[SYMBOL_ASYNC_ITERATOR]) ||
asyncIterable['@@asyncIterator']
if (typeof method === 'function') {
return method
}
}
}
exports.getAsyncIteratorMethod = getAsyncIteratorMethod
/**
* Similar to `getAsyncIterator()`, this method returns a new AsyncIterator
* given an AsyncIterable. However it will also create an AsyncIterator for a
* non-async Iterable as well as non-Iterable Array-like collection, such as
* Array in a pre-ES2015 environment.
*
* `createAsyncIterator` is complimentary to `forAwaitEach`, but allows a
* buffering "pull"-based iteration as opposed to `forAwaitEach`'s
* "push"-based iteration.
*
* `createAsyncIterator` produces an AsyncIterator for non-async Iterables as
* described in the ECMAScript proposal [Async-from-Sync Iterator Objects](https://tc39.github.io/proposal-async-iteration/#sec-async-from-sync-iterator-objects).
*
* > Note: Creating `AsyncIterator`s requires the existence of `Promise`.
* > While `Promise` has been available in modern browsers for a number of
* > years, legacy browsers (like IE 11) may require a polyfill.
*
* @example
*
* var createAsyncIterator = require('iterall').createAsyncIterator
*
* var myArraylike = { length: 3, 0: 'Alpha', 1: 'Bravo', 2: 'Charlie' }
* var iterator = createAsyncIterator(myArraylike)
* iterator.next().then(console.log) // { value: 'Alpha', done: false }
* iterator.next().then(console.log) // { value: 'Bravo', done: false }
* iterator.next().then(console.log) // { value: 'Charlie', done: false }
* iterator.next().then(console.log) // { value: undefined, done: true }
*
* @template T the type of each iterated value
* @param {AsyncIterable|Iterable|{ length: number }} source
* An AsyncIterable, Iterable, or Array-like object to produce an Iterator.
* @return {AsyncIterator} new AsyncIterator instance.
*/
function createAsyncIterator(source) {
if (source != null) {
var asyncIterator = getAsyncIterator(source)
if (asyncIterator) {
return asyncIterator
}
var iterator = createIterator(source)
if (iterator) {
return new AsyncFromSyncIterator(iterator)
}
}
}
exports.createAsyncIterator = createAsyncIterator
// When the object provided to `createAsyncIterator` is not AsyncIterable but is
// sync Iterable, this simple wrapper is created.
function AsyncFromSyncIterator(iterator) {
this._i = iterator
}
// Note: all AsyncIterators are themselves AsyncIterable.
AsyncFromSyncIterator.prototype[$$asyncIterator] = function() {
return this
}
// A simple state-machine determines the IteratorResult returned, yielding
// each value in the Array-like object in order of their indicies.
AsyncFromSyncIterator.prototype.next = function() {
var step = this._i.next()
return Promise.resolve(step.value).then(function(value) {
return { value: value, done: step.done }
})
}
/**
* Given an object which either implements the AsyncIterable protocol or is
* Array-like, iterate over it, calling the `callback` at each iteration.
*
* Use `forAwaitEach` where you would expect to use a `for-await-of` loop.
*
* Similar to [Array#forEach][], the `callback` function accepts three
* arguments, and is provided with `thisArg` as the calling context.
*
* > Note: Using `forAwaitEach` requires the existence of `Promise`.
* > While `Promise` has been available in modern browsers for a number of
* > years, legacy browsers (like IE 11) may require a polyfill.
*
* @example
*
* var forAwaitEach = require('iterall').forAwaitEach
*
* forAwaitEach(myIterable, function (value, index, iterable) {
* console.log(value, index, iterable === myIterable)
* })
*
* @example
*
* // ES2017:
* for await (let value of myAsyncIterable) {
* console.log(await doSomethingAsync(value))
* }
* console.log('done')
*
* // Any JavaScript environment:
* forAwaitEach(myAsyncIterable, function (value) {
* return doSomethingAsync(value).then(console.log)
* }).then(function () {
* console.log('done')
* })
*
* @template T the type of each iterated value
* @param {AsyncIterable|Iterable | T>|{ length: number }} source
* The AsyncIterable or array to iterate over.
* @param {function(T, number, object)} callback
* Function to execute for each iteration, taking up to three arguments
* @param [thisArg]
* Optional. Value to use as `this` when executing `callback`.
*/
function forAwaitEach(source, callback, thisArg) {
var asyncIterator = createAsyncIterator(source)
if (asyncIterator) {
var i = 0
function next() {
return asyncIterator.next().then(function(step) {
if (!step.done) {
return Promise.resolve(
callback.call(thisArg, step.value, i++, source)
).then(next)
}
})
}
return next()
}
}
exports.forAwaitEach = forAwaitEach