Lazy | /lib/lazy.ts | lazy@v1.7.3

class Lazy

implements Iterable<TElement>

Abstract

import { Lazy } from "https://deno.land/x/lazy@v1.7.3/lib/lazy.ts";

The base class that all lazy iterable objects derive from. This can be extended with custom iterators if needed.

Methods

aggregate(agg: AggFn<TElement, TElement>): TElement

Applies an accumulator function over an interable.

aggregate<TAcc>(agg: AggFn<TElement, TAcc>, seed: TAcc): TAcc

Applies an accumulator function over an interable.

all(predicate: BoolPredicate<TElement>): boolean

Returns whether all elements satisfy the given condition.

any(): boolean

Returns whether the iterable is not empty.

any(predicate: BoolPredicate<TElement>): boolean

Returns whether any of the elements satisfy the given condition.

append(element: TElement): Lazy<TElement>

Appends the element to the end of the iterable.

apply<TLazy extends Lazy<TResult>, TResult = TElement>(fn: (t: Lazy<TElement>) => TLazy): Lazy<TResult>

Applies the given lazy iterable implementation to the current object. This allows for using custom Lazy implementations using the standard chaining syntax.

average(): TElement extends number ? number : never

Computes the average of the iterable.

average(selector: MapFn<TElement, number>): number

Computes the average of result of the selector function over the iterable.

batchIn(batchSize: number, includeIncomplete?): Lazy<Iterable<TElement>>

Batches elements in groups of the given batch size.

cache(): Lazy<TElement>

Resolves the underlaying iterable completely and returns a lazy of the result.

concat(...iterables: Array<Iterable<TElement>>): Lazy<TElement>

Concatinates multiple iterables in order.

contains(element: TElement, comparer?: ComparerFn<TElement>): boolean

Determines whether the iterable has a given element.

count(): number

Returns the number of elements in the iterable.

count(predicate: BoolPredicate<TElement>): number

Returns the number of elements that satify the given condition.

defaultIfEmpty(defaultValue: TElement): Lazy<TElement>

Returns the elements in the iterable, or the given default value as the only element if it contained none.

distinct<TKey>(compareOn?: MapFn<TElement, TKey>): Lazy<TElement>

Returns the distinct elements in the iterable.

elementAt(index: number): TElement

Returns the element at the given index of the iterable.

elementAtOrDefault(index: number, defaultValue: TElement): TElement

Returns the element at the given index of the iterable, or the given default value if out of range.

elementAtOrDefault<TDefault>(index: number, defaultValue: TDefault): TElement | TDefault

Returns the element at the given index of the iterable, or the given default value if out of range.

except<TKey = TElement>(second: Iterable<TElement>, compareOn?: MapFn<TElement, TKey>): Lazy<TElement>

Returns the set difference between 2 iterables. This like doing an XOR over the 2 iterables.

first(): TElement

Returns the first element in the iterable.

first(predicate: BoolPredicate<TElement>): TElement

Returns the first element that satisfies the given condition.

firstOrDefault(defaultValue: TElement): TElement

Returns the first element in the iterable, or the given default value if the iterable was empty.

firstOrDefault<TDefault>(defaultValue: TDefault): TElement | TDefault

Returns the first element in the iterable, or the given default value if the iterable was empty.

firstOrDefault(defaultValue: TElement, predicate: BoolPredicate<TElement>): TElement

Returns the first element in the iterable that satisfies the condition, or the given default value.

firstOrDefault<TDefault>(defaultValue: TDefault, predicate: BoolPredicate<TElement>): TElement | TDefault

Returns the first element in the iterable that satisfies the condition, or the given default value.

forEach(callbackFn: CallbackFn<TElement>): void

Mimics the behaviour of Array.prototype.forEach, with the exception of not providing the entire array as the 3rd param of the callback.

groupBy<TKey>(keyFn: MapFn<TElement, TKey>): Lazy<IGrouping<TKey, TElement>>

Groups the elements by key.

groupBy<TKey, TItem>(keyFn: MapFn<TElement, TKey>, elementSelector: MapFn<TElement, TItem>): Lazy<IGrouping<TKey, TItem>>

Groups the elements by key and projects each element using the given function.

groupBy<TKey, TItem, TResult>(

keyFn: MapFn<TElement, TKey>,

elementSelector: MapFn<TElement, TItem>,

resultSelector: CombineFn<TKey, Iterable<TItem>, TResult>,

): Lazy<TResult>

Groups the elements by key and projects each element using the given function. The elements of each group are projected using the given function.

groupJoin<TSecond, TKey, TResult>(

second: Iterable<TSecond>,

firstKeyFn: MapFn<TElement, TKey>,

secondKeyFn: MapFn<TSecond, TKey>,

joinFn: CombineFn<TElement, Iterable<TSecond>, TResult>,

): Lazy<TResult>

Joins 2 iterables on the given key and groups the results.

intersect<TKey = TElement>(second: Iterable<TElement>, compareOn?: MapFn<TElement, TKey>): Lazy<TElement>

Returns the set intersection between 2 iterables. This like doing an AND over the 2 iterables.

iterableEquals(second: Iterable<TElement>, comparer?: ComparerFn<TElement>): boolean

Determines whether 2 iterables are equal.

join<TSecond, TKey, TResult>(

second: Iterable<TSecond>,

firstKeyFn: MapFn<TElement, TKey>,

secondKeyFn: MapFn<TSecond, TKey>,

joinFn: CombineFn<TElement, TSecond, TResult>,

): Lazy<TResult>

Joins 2 iterables on the given matching keys. This is similar to a JOIN in SQL.

last(): TElement

Returns the last element in the iterable.

last(predicate: BoolPredicate<TElement>): TElement

Returns the last element in the iterable that satisfies the given condition.

lastOrDefault(defaultValue: TElement): TElement

Returns the last element in the iterable, or the given default value if the iterable was empty.

lastOrDefault<TDefault>(defaultValue: TDefault): TElement | TDefault

Returns the last element in the iterable, or the given default value if the iterable was empty.

lastOrDefault(defaultValue: TElement, predicate: BoolPredicate<TElement>): TElement

Returns the last element in the iterable that satisfies the given condition, or the given default value.

lastOrDefault<TDefault>(defaultValue: TDefault, predicate: BoolPredicate<TElement>): TElement | TDefault

Returns the last element in the iterable that satisfies the given condition, or the given default value.

max(): TElement extends number ? number : never

Returns the maximum value in the iterable.

max(selector: MapFn<TElement, number>): number

Returns the maximum value of result of the selector function over the iterable.

min(): TElement extends number ? number : never

Returns the minimum value in the iterable.

min(selector: MapFn<TElement, number>): number

Returns the minimum value of result of the selector function over the iterable.

orderBy<TKey>(keyFn: MapFn<TElement, TKey>, compareFn?: SortFn<TKey>): Lazy<TElement>

Sorts the iterable in ascending order.

orderByDecending<TKey>(keyFn: MapFn<TElement, TKey>, compareFn?: SortFn<TKey>): Lazy<TElement>

Sorts the iterable in descending order.

orderNumericallyBy(keyFn: MapFn<TElement, number>): Lazy<TElement>

Sorts the iterable in acending order according to the numeric result of the key function.

orderNumericallyByDecending(keyFn: MapFn<TElement, number>): Lazy<TElement>

Sorts the iterable in descending order according to the numeric result of the key function.

prepend(element: TElement): Lazy<TElement>

Prepends the element to the beginning of the iterable.

resolveAll(): Promise<TElement extends PromiseLike<infer TResult> ? Lazy<TResult> : Lazy<TElement>>

Resolves all of the promises in the iterable, and returns a new Lazy iterable from the result.

reverse(): Lazy<TElement>

Reverses the order of the iterable.

select<TResult>(selector: IndexMapFn<TElement, TResult>): Lazy<TResult>

Projects the elements of the iterable into a new form.

selectMany<TResult>(selector: IndexMapFn<TElement, Iterable<TResult>>): Lazy<TResult>

Projects the elements of the iterable into a new form, and flattens the iterable of iterables into a single iterable.

single(predicate: BoolPredicate<TElement>): TElement

Returns a single element from the iterable that matches the given condition.

singleOrDefault(predicate: BoolPredicate<TElement>, defaultValue: TElement): TElement

Returns a single element from the iterable that matches the given condition, or a default value if no element was found.

singleOrDefault<TDefault>(predicate: BoolPredicate<TElement>, defaultValue: TDefault): TElement | TDefault

Returns a single element from the iterable that matches the given condition, or a default value if no element was found.

skip(count: number): Lazy<TElement>

Skips the given number of elements from the start of the iterable and returns the rest.

skipLast(count: number): Lazy<TElement>

Skips the given number of elements from the end of the iterable, returning the rest.

skipWhile(predicate: IndexPredicate<TElement>): Lazy<TElement>

Skips all elements in the iterable until the condition returns true, after which all elements are returned regardless.

stringJoin(separator?: string, strFn?: StrFn<TElement>): string

Joins all the elements in the iterable together into a single string, split by the given separator.

sum(): TElement extends number ? number : never

Computes the sum of all the elements in the iterable.

sum(selector: MapFn<TElement, number>): number

Returns the sum of all the results of the selector function over the iterable.

take(count: number): Lazy<TElement>

Returns the given number of elements from the start of the iterable, ignoring the rest.

takeLast(count: number): Lazy<TElement>

Returns the given number of elements from the end of the iterable, ignore the elements before.

takeWhile(predicate: IndexPredicate<TElement>): Lazy<TElement>

Takes all elements in the iterable until the condition returns true, after which the iterable is considered to have ended.

toArray(): TElement[]

Converts the iterable into a standard JavaScript Array.

toJSON(): TElement[]

Converts the iterable to a JSON-serialisable array.

toMap<TKey, TResult = TElement>(keyFn: MapFn<TElement, TKey>, valueFn?: MapFn<TElement, TResult>): Map<TKey, TResult>

Converts the iterable into a map using the key and value function.

union<TKey = TElement>(second: Iterable<TElement>, compareOn?: MapFn<TElement, TKey>): Lazy<TElement>

Returns the set union between 2 iterables. This like doing an OR over the 2 iterables.

where<TResult extends TElement>(predicate: IndexIsPredicate<TElement, TResult>): Lazy<TResult>

Filters elements based on the given predicate.

where(predicate: IndexPredicate<TElement>): Lazy<TElement>

Filters elements based on the given predicate.

zip<TSecond>(second: Iterable<TSecond>): Lazy<[TElement, TSecond]>

Combines 2 iterables into an iterable of tuples. This will merge elements on the same index, finishing on the iterable that finishes first. If the first iterable has 3 elements, and the second 4, then the result will have 3 elements.

zip<TSecond, TResult>(second: Iterable<TSecond>, selector: CombineFn<TElement, TSecond, TResult>): Lazy<TResult>

Combines 2 iterables using the given selector. This will merge elements on the same index, finishing on the iterable that finishes first. If the first iterable has 3 elements, and the second 4, then the result will have 3 elements.

abstract

[Symbol.iterator](): Iterator<TElement>

Static Methods

empty<TElement>(): Lazy<TElement>

Creates an empty lazy iterable.

from<TElement>(iterable: Iterable<TElement>): Lazy<TElement>

Creates a lazy iterable object from the given iterable object.

range(start: number, end?: number): Lazy<number>

Creates a lazy iterable object that will produce a range of integers.

repeat<TElement>(element: TElement, count?: number): Lazy<TElement>

Creates a lazy iterable object that will repeate the element a given number of times.

Type Parameters

Methods

Static Methods