partition
signature: partition(predicate: function: boolean, thisArg: any): [Observable, Observable]
Split one observable into two based on provided predicate.
Examples
Example 1: Split even and odd numbers
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import { from } from 'rxjs/observable/from';
import { partition, map } from 'rxjs/operators';
const source = from([1, 2, 3, 4, 5, 6]);
//first value is true, second false
const [evens, odds] = source.pipe(partition(val => val % 2 === 0));
/*
Output:
"Even: 2"
"Even: 4"
"Even: 6"
"Odd: 1"
"Odd: 3"
"Odd: 5"
*/
const subscribe = merge(
evens.pipe(map(val => `Even: ${val}`)),
odds.pipe(map(val => `Odd: ${val}`))
).subscribe(val => console.log(val));
Example 2: Split success and errors
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jsFiddle )
import { from } from 'rxjs/observable/from';
import { of } from 'rxjs/observable/of';
import { merge } from 'rxjs/observable/merge';
import { map, partition, catchError } from 'rxjs/operators';
const source = from([1, 2, 3, 4, 5, 6]);
//if greater than 3 throw
const example = source.pipe(
map(val => {
if (val > 3) {
throw `${val} greater than 3!`;
}
return { success: val };
}),
catchError(val => of({ error: val }))
);
//split on success or error
const [success, error] = example.pipe(partition(res => res.success));
/*
Output:
"Success! 1"
"Success! 2"
"Success! 3"
"Error! 4 greater than 3!"
*/
const subscribe = merge(
success.pipe(map(val => `Success! ${val.success}`)),
error.pipe(map(val => `Error! ${val.error}`))
).subscribe(val => console.log(val));
Additional Resources
- partition
- Official docs
Source Code:
https://github.com/ReactiveX/rxjs/blob/master/src/internal/operators/partition.ts