split-if

RxJS operator. Packs all the source Observable values into arrays. New array is emitted every time a predicate is fulfilled.

See RxJS

Examples

Example 1 (split by value)

const {from} = require('rxjs');
const {splitIf} = require('split-if');

const src = from([4, 8, 1, 3, 5, 1, 1, 6, 8]).pipe(splitIf(x => x === 1));
const res = [];
src.subscribe(x => res.push(x));
console.log(res);
//=> [ [ 4, 8 ], [ 1, 3, 5 ], [ 1 ], [ 1, 6, 8 ] ]

Example 2 (split by index)

We can easily make a partitionN RxJS operator using splitIf:

import {OperatorFunction} from 'rxjs';
import {splitIf} from 'split-if';

const partitionN = <T>(n: number): OperatorFunction<T, T[]> =>
  splitIf((_: T, i: number) => i % n === 0);

Let's use it:

import {from} from 'rxjs';

const src = from([4, 8, 1, 3, 5, 4, 1, 6, 8, -1, 2]).pipe(partitionN(3));
const res: number[][] = [];
src.subscribe((x: number[]) => res.push(x));
console.log(res);
//=> [ [ 4, 8, 1 ], [ 3, 5, 4 ], [ 1, 6, 8 ], [ -1, 2 ] ]

Why to use

• Typed. With d.ts for Javascript.
• Well tested. 100% code coverage.

Installation

$ npm install split-if

Usage

Typescript / ES module:

import {splitIf} from 'split-if';

Javascript / CommonJS:

const {splitIf} = require('split-if');

API

function splitIf<T>(
  predicate: (value: T, index: number) => boolean,
  thisArg?: any
): OperatorFunction<T, T[]>;

Where its OperatorFunction<T, T[]> can be substituted for:

(source: Observable<T>) => Observable<T[]>;

See: RxJS OperatorFunction

Parameters

T	{any}	The type of Observable's value.
predicate	{(value: T, index: number) => boolean}	A function that evaluates each value emitted by the source Observable. If it returns true, a new array of previous 'buffered' values is emitted. The index parameter is the number i for the i-th source emission that has happened since the subscription, starting from the number 0.
thisArg	{any}	Optional. Default is undefined. An optional argument to determine the value of this in the predicate function.

Returns

A function that returns an Observable that emits arrays of all items from the source Observable. These arrays are emitted every time a predicate is fulfilled.