/
lastOrDefault.ts
39 lines (34 loc) · 1.38 KB
/
lastOrDefault.ts
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/*
* @author electricessence / https://github.com/electricessence/
* @license MIT
*/
import { IterableTransform } from '../IterableTransform';
/**
* An iterable transform that returns the last element of a sequence, or `undefined` if no element is found.
* @return {IterableTransform<T, T | undefined>}
*/
export default function lastOrDefault<T>(): IterableTransform<T, T | undefined>;
/**
* An iterable transform that returns the last element of a sequence, or the default value if no element is found.
* @param {TDefault} defaultValue
* @return {IterableTransform<T, T | TDefault>}
*/
export default function lastOrDefault<T, TDefault>(defaultValue: TDefault): IterableTransform<T, T | TDefault>;
/**
* An iterable transform that returns the last element of a sequence, or a default value if no element is found.
* @param {TDefault} defaultValue
* @return {IterableTransform<T, T | TDefault | undefined>}
*/
export default function lastOrDefault<T, TDefault>(defaultValue?: TDefault): IterableTransform<T, T | TDefault | undefined> {
return function (sequence: Iterable<T>): T | TDefault | undefined {
if (!sequence) return defaultValue;
if (sequence instanceof Array) {
return sequence.length == 0
? defaultValue
: sequence[sequence.length - 1];
}
let last: T | TDefault | undefined = defaultValue;
for (const current of sequence) last = current;
return last;
};
}