[RxJS] Transformation operator: scan
2016-05-27 04:36
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All of the combination operators take two or more observables as input. These operators may also be alternatively called "vertical combination operators", because of how they work in a marble diagram. Next, we will learn about scan(), which is an important "horizontal combination operator".
var click$ = Rx.Observable.fromEvent(document.querySelector("#btn"), 'click'); /* ----ev-----ev---ev----ev----ev----.. mapTo(1) ----1 -----1 ---1 ----1 ----1-----.. scan( (acc, curr) => acc + curr, 0) ----1------2----3-----4-----5-----.. */ var clicks$ = click$ .mapTo(1) .scan( (acc, curr) => { return acc + curr }, 0); var sub = clicks$.subscribe( (x) => console.debug("Total Clicks: " + x), (err) => console.error(err), () => console.info("DONE") )
var foo$ = Rx.Observable.of('h', 'e', 'l', 'l', 'o') .zip(Rx.Observable.interval(500), (c, t) => c); var bar$ = foo$.scan( (acc, curr) => { return acc + curr; }, ''); /* -----h-----e-----l-----l------o| (foo) scan( (acc, curr) => acc + curr, '') -----h-----(he)--(hel)-(hell)-(hello|) (bar) */ var sub = bar$.subscribe( (x) => console.debug(x), (err) => console.error(err), () => console.info("DONE") ); /** "h" "he" "hel" "hell" "hello" "DONE" */
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