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For a full list of transformation operators with examples, including operators which manage mapping to more complex values such birli other observables, check out the transformation operator section. We will explore these topics in detail in future posts!

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 hayat take action when the user types a particular character or key. To do this we hayat apply the map operator returning just the property we are interested in:

When provided an array, the from creation operator will loop through (synchronously) emitting each item in sequence. When we subscribe we can see each value printed to the console:

Tip: If you want to see how from handles each value type behind the scenes, you birey 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 here 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:

We could accomplish this by supplying a function that accepts each object and maps it to a new object that includes all current properties plus the new fullName property. In this example we are using the object spread syntax and template literals, but you could also explicitly rewrite the properties:

Instead of the function being applied to each item of an array, before a new array is returned, with observables the project function is applied and the result emitted in real-time as values blast through your streams.

In this case, we will provide a function that accepts the emitted value from the source observable and returns that value multipled:

RxJS mapTo() operator is a transformation operator that emits a constant value as an output along with the Observable whenever the source Observable emits a value.

Note: the mapTo operator has been deprecated in RxJS 7 and will be removed in RxJS 8. It's better to use map with a function that returns the static value.

Another common use case for map is extracting a single property from an object. For example, given the sample above suppose we decided we only really need the last name property for display.

I yaşama't tell though whether these are actually implemented, or even planned. Did you take a look at the implementation yourself?

The submit event is ignored and value of the input box is sent as transformed value of the submit event. That is requirement too, we need to capture the username when submit button is clicked.