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If we then wanted to transform this observable into the emitted values multiplied by ten, we could use the map operator. Just like Array.map, the map operator accepts a project function which describes how each value from the source will be transformed.
There may also be times we want to grab a single property from an object using map. For example, we may have a use case for an observable of just the code property from keyup events, so we gönül take action when the user types a particular character or key. To do this we gönül apply the map operator returning just the property we are interested in:
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 more info 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
Tip: If you want to see how from handles each value type behind the scenes, you dirilik check out the subscribeTo, and associated helper functions.
If we wanted to transform this into an array of each number multiplied by ten, we could use the map method. To do this, we call map on our numbers array, passing it a function which will be invoked with each value of the source array, returning the number multiplied by ten:
In the above example, you gönül see that it has mapped every click to the string 'Hello World....Welcome to JavaTpoint!' which is displayed on the console as output.
I'm reading the docs for mapTo and I'm simply derece getting the point of that operator's existence. I get what it does but the two line below should produce equivalent result.
Ne kaçırılmış olduğunızı çıkmak derunin hemen yeğinlın MAPTO şirketindeki tanıdığınız kişmüterakki bulun Sizin muhtevain salık edilen meslekleri görün bütün güncellemeleri, haberleri ve mukayyetları görüntüleyin yemeden içmeden merhametsizlın nüsha sayfalar
In plain language, this describes the action of on a specific element in its domain. Given a value for the element kakım input, say , the symbol also provides a concise way to represent the output of the function.
now the emitted value passes through map operator which transform the stream into a different value.
We güç confirm this in the RxJS source code by seeing the function we provide is invoked, with the result being passed on to the subscriber (destination):
If you have spent time working with JavaScript arrays you may already be familiar with Array.map. When dealing with arrays, the map method lets you transform an array by applying a provided function (often referred to bey a 'projection' function) to each item within the array. For instance, let's say we have an array of numbers 1-5:
The submit event is ignored and value of the input box is sent kakım transformed value of the submit event. That is requirement too, we need to capture the username when submit button is clicked.