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August 23, 2017 00:54
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Examples for https://medium.com/p/651f4b7d45cf/edit
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| // An observable that emits 10 multiples of 100 every 1 second | |
| const source$ = Observable.interval(1000) | |
| .take(10) | |
| .map(x => x * 100); | |
| /** | |
| * returns a promise that waits `ms` milliseconds and emits "done" | |
| */ | |
| function promiseDelay(ms) { | |
| return new Promise(resolve => { | |
| setTimeout(() => resolve('done'), ms); | |
| }); | |
| } | |
| // using it in a switchMap | |
| source$.switchMap(x => promiseDelay(x)) // works | |
| .subscribe(x => console.log(x)); | |
| source$.switchMap(promiseDelay) // just a little more terse | |
| .subscribe(x => console.log(x)); | |
| // or takeUntil | |
| source$.takeUntil(doAsyncThing('hi')) // totally works | |
| .subscribe(x => console.log(x)) | |
| // or weird stuff you want to do like | |
| Observable.of(promiseDelay(100), promiseDelay(10000)).mergeAll() | |
| .subscribe(x => console.log(x)) |
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| function getErroringPromise() { | |
| console.log('getErroringPromise called'); | |
| return Promise.reject(new Error('sad')); | |
| } | |
| Observable.defer(getErroringPromise) | |
| .retry(3) | |
| .subscribe(x => console.log); | |
| // logs "getErroringPromise called" 4 times (once + 3 retries), then errors |
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| Observable.defer(async function() { | |
| const a = await Promise.resolve(1); | |
| const b = a + await Promise.resolve(2); | |
| return a + b + await Promise.resolve(3); | |
| }) | |
| .subscribe(x => console.log(x)) // logs "7" |
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| const button = document.querySelector('button'); | |
| const click$ = Observable.fromEvent(button, 'click'); | |
| /** | |
| * Waits for 10 clicks of the button | |
| * then posts a timestamp of the tenth click to an endpoint | |
| * using fetch | |
| */ | |
| async function doWork() { | |
| await click$.take(10) | |
| .map((_, i) => i + 1) | |
| .forEach(n => console.log(`click ${n}`)); | |
| return await fetch( | |
| 'notify/tenclicks', | |
| { method: 'POST', body: Date.now() } | |
| ); | |
| } | |
| doWork(); |
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| const source$ = Observable.interval(1000).take(3); // emits 0, 1, 2 | |
| // waits 3 seconds, then logs "2". | |
| // because the observable takes 3 seconds to complete, and | |
| // the interval emits incremented numbers starting at 0 | |
| async function test() { | |
| console.log(await source$.toPromise()); | |
| } | |
| test(); |
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