42 lines
1.6 KiB
JavaScript
42 lines
1.6 KiB
JavaScript
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import { ArrayObservable } from '../observable/ArrayObservable';
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import { ScalarObservable } from '../observable/ScalarObservable';
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import { EmptyObservable } from '../observable/EmptyObservable';
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import { concat as concatStatic } from '../observable/concat';
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import { isScheduler } from '../util/isScheduler';
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/* tslint:enable:max-line-length */
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/**
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* Returns an Observable that emits the items you specify as arguments before it begins to emit
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* items emitted by the source Observable.
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*
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* <img src="./img/startWith.png" width="100%">
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*
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* @param {...T} values - Items you want the modified Observable to emit first.
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* @param {Scheduler} [scheduler] - A {@link IScheduler} to use for scheduling
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* the emissions of the `next` notifications.
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* @return {Observable} An Observable that emits the items in the specified Iterable and then emits the items
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* emitted by the source Observable.
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* @method startWith
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* @owner Observable
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*/
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export function startWith(...array) {
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return (source) => {
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let scheduler = array[array.length - 1];
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if (isScheduler(scheduler)) {
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array.pop();
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}
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else {
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scheduler = null;
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}
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const len = array.length;
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if (len === 1) {
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return concatStatic(new ScalarObservable(array[0], scheduler), source);
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}
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else if (len > 1) {
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return concatStatic(new ArrayObservable(array, scheduler), source);
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}
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else {
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return concatStatic(new EmptyObservable(scheduler), source);
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}
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};
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}
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//# sourceMappingURL=startWith.js.map
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