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takeLast.ts
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takeLast.ts
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import { Operator, Observer } from '../index';
import { createSource } from '../sources';
import subscribe from '../utils/subscribe';
/**
* Emits only the last count values emitted by the source
*
* @param count - number of values to emit
* @return callbag operator
*
* @public
*/
function takeLast<I>(count = 1): Operator<I, I> {
return source => {
return createSource((next, complete, error) => {
const lastValues: I[] = [];
const observer: Observer<I> = {
next: value => {
lastValues.push(value);
if (lastValues.length > count) {
lastValues.shift();
}
},
error,
complete: () => {
for (let i = 0, l = lastValues.length; i < l; i += 1) {
next(lastValues[i]);
}
complete();
},
};
return subscribe(source)(observer);
});
};
}
export default takeLast;