RxJS is a JavaScript library that enables the creation of asynchronous and event-based programs. The main type is the Observable
and a suite of functions and operators are provided to make it easier to work with the data coming through. This series will detail those operators (and a few stand-alone functions) and provide examples of their use.
In this post, we’re going to cover the bufferCount
operator.
What does it do?
The bufferCount
operator is used to batch a certain number of values together. When we add bufferCount
to our pipeline we pass it a number that indicates the number of values to batch. Once enough values have been received, bufferCount
will combine all values into an array and send them through the pipeline.
Example
import { bufferCount, interval } from 'rxjs';
interval(1000)
.pipe(bufferCount(10))
.subscribe(x => {
console.log(x);
});
We’re using interval
to provide us with incrementing numbers every second. When we add bufferCount
we’re telling it to wait for 10 values, so every time it receives 10 from interval
an array will be sent down the pipeline. Running this will print:
[
0, 1, 2, 3, 4,
5, 6, 7, 8, 9
]
[
10, 11, 12, 13, 14,
15, 16, 17, 18, 19
]
If the original observable completes the buffer will send whatever values it has collected through the pipeline immediately.
The source code for this example is available on GitHub:
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