how to use the reduce function from the rxjs library in javascript

The reduce function from the rxjs library in JavaScript is used to apply a function to each element emitted by an Observable, sequentially, and emit the final accumulated result.

Here's an example:

index.tsx
const { from } = require('rxjs');
const { reduce } = require('rxjs/operators');

const nums = from([1, 2, 3, 4, 5]);
const sumReducer = (acc, currentValue) => acc + currentValue;

nums.pipe(
  reduce(sumReducer)
).subscribe(result => console.log(result)); // Output: 15
270 chars
10 lines

In the above example, we're creating an Observable nums from an array [1,2,3,4,5]. We're then using the reduce operator to apply the sumReducer function to each value emitted by nums. In this case, sumReducer is just a simple function that adds the current value to the accumulated total.

Finally, we subscribe to the resulting Observable and log the final result to the console. The output is 15, which is the sum of all the numbers in the array.

Note that the reduce function is an operator in rxjs, so we need to import it using rxjs/operators.