Değil Hakkında Detaylar bilinen mapto
Değil Hakkında Detaylar bilinen mapto
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To do this we could apply the map operator, providing a function that returns an object with just these properties:
import fromEvent from 'rxjs'; import mapTo from 'rxjs/operators'; //emit every click on document const source = fromEvent(document, 'click'); //map all emissions check here to one value const example = source.
Similar to our array example with objects, we may also want to transform an observable of objects with the map operator. For instance, suppose we have an observable of click events that we wish to transform into an observable of objects containing just the clientX and clientY coordinates of these events.
前言 操作符 组合 combineAll combineLatest concat concatAll forkJoin merge mergeAll pairwise race startWith withLatestFrom zip 条件 defaultIfEmpty every 创建 create empty from fromEvent fromPromise interval of range throw timer 错误处理 catchError retry retryWhen 多播 publish multicast share shareReplay 过滤 debounce debounceTime distinctUntilChanged filter first ignoreElements last sample single skip skipUntil skipWhile take takeUntil takeWhile throttle throttleTime 转换 buffer bufferCount bufferTime bufferToggle bufferWhen concatMap concatMapTo exhaustMap expand exhaustMap groupBy map mapTo mergeMap partition pluck reduce scan switchMap window windowCount windowTime windowToggle windowWhen 工具 do delay delayWhen dematerialize let timeout toPromise 完整列表 食谱 智能计数器 进度条 游戏循环 概念 RxJS v5 -> v6 升级 理解操作符导入
Lastly, there may also be times where you always want to map to a single value, no matter the input. For these situations, you birey use the mapTo operator.
While the real implementation of Array.map includes features like index tracking and proper error management, this gives us a general sense of how things work behind the scenes.
In the above example, you sevimli see that it has mapped every click to the string 'Hello World....Welcome to JavaTpoint!' which is displayed on the console bey output.
Like many other helper operators in RxJS, behind the scenes pluck is simply reusing the map operator, passing it a function to grab the appropriate property:
In this case, we will provide a function that accepts the emitted value from the source observable and returns that value multipled:
In plain language, this describes the action of on a specific element in its domain. Given a value for the element as input, say , the symbol also provides a concise way to represent the output of the function.
The pluck operator accepts a list of values which describe the property you wish to grab from the emitted item. For instance, using our event code example from above we could use pluck instead of map to extract the code property from the event object:
On the other hand map: Returns a list containing the results of applying the given transform function to each element in the original array.
RxJS features many operators that are simply shortcuts for other operators. For example, any time we just want to grab a single property from an emitted value, instead of using map we could use pluck.
2 github.com/ReactiveX/rxjs/blob/master/src/internal/operators/… source] sums it up; I mean technically I suppose it's fractionally faster since it doesn't increment the index :shrug: github.com/ReactiveX/rxjs/blob/master/src/internal/operators/…
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