67 lines
1.3 KiB
TypeScript
67 lines
1.3 KiB
TypeScript
|
/**
|
||
|
|
* @packageDocumentation
|
||
|
|
*
|
||
|
|
* Return the last value from an (async)iterable.
|
||
|
|
*
|
||
|
|
* @example
|
||
|
|
*
|
||
|
|
* ```javascript
|
||
|
|
* import last from 'it-last'
|
||
|
|
*
|
||
|
|
* // This can also be an iterator, generator, etc
|
||
|
|
* const values = [0, 1, 2, 3, 4]
|
||
|
|
*
|
||
|
|
* const res = last(values)
|
||
|
|
*
|
||
|
|
* console.info(res) // 4
|
||
|
|
* ```
|
||
|
|
*
|
||
|
|
* Async sources must be awaited:
|
||
|
|
*
|
||
|
|
* ```javascript
|
||
|
|
* import last from 'it-last'
|
||
|
|
*
|
||
|
|
* const values = async function * () {
|
||
|
|
* yield * [0, 1, 2, 3, 4]
|
||
|
|
* }
|
||
|
|
*
|
||
|
|
* const res = await last(values())
|
||
|
|
*
|
||
|
|
* console.info(res) // 4
|
||
|
|
* ```
|
||
|
|
*/
|
||
|
|
|
||
|
|
function isAsyncIterable <T> (thing: any): thing is AsyncIterable<T> {
|
||
|
|
return thing[Symbol.asyncIterator] != null
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Returns the last item of an (async) iterable, unless empty, in which case
|
||
|
|
* return `undefined`
|
||
|
|
*/
|
||
|
|
function last <T> (source: Iterable<T>): T | undefined
|
||
|
|
function last <T> (source: Iterable<T> | AsyncIterable<T>): Promise<T | undefined>
|
||
|
|
function last <T> (source: Iterable<T> | AsyncIterable<T>): Promise<T | undefined> | T | undefined {
|
||
|
|
if (isAsyncIterable(source)) {
|
||
|
|
return (async () => {
|
||
|
|
let res
|
||
|
|
|
||
|
|
for await (const entry of source) {
|
||
|
|
res = entry
|
||
|
|
}
|
||
|
|
|
||
|
|
return res
|
||
|
|
})()
|
||
|
|
}
|
||
|
|
|
||
|
|
let res
|
||
|
|
|
||
|
|
for (const entry of source) {
|
||
|
|
res = entry
|
||
|
|
}
|
||
|
|
|
||
|
|
return res
|
||
|
|
}
|
||
|
|
|
||
|
|
export default last
|