Description

This project is inspired by library as RamdaJS and try to help developers to be more expressive on handling events with these operators.

How to use it

Requirements

• These operators are designated to project that use RxJs 6+

filters

filterNotNull

• This operator will filter values that are not null

    of(null, { color: 'red' })
    .pipe(filterNotNull())
    .subscribe(value => console.log(value));

• The result will be: { color: red }

filterNull

• This operator will filter only values are null

    of(null, { color: 'red' })
    .pipe(filterNull())
    .subscribe(value => console.log(value));

• The output will be: null

filterPropNotNull

• Filter by property that are not null

of({ color: null }, { color: 'red' })
    .pipe(filterPropNotNull('color'))
    .subscribe(value => console.log(value));

• The output will be: { color: 'red' }

map

mapIfFalse

• Map if the predicate are false

of({ color: null }, { color: 'red' }).pipe(
    mapIfFalse(
        ({ color }) => color !== null, // predicate 
        ({ color }) => color // ifFalse
    )
)
.subscribe(value => console.log(value));

• The output will be: red

mapIfTrue

• Map if the predicate are true

of({ color: 'yellow' }, { color: 'red' }).pipe(
    mapIfTrue(
        ({ color }) => color === 'red', // predicate 
        ({ color }) => color // ifTrue
    )
)
.subscribe(value => console.log(value));

• The output will be: red

mapIfOrElse

• Using this operator you can use if/else in the map, for example:

of({ color: 'yellow' }, { color: 'red' }).pipe(
    mapIfOrElse(
        ({ color }) => color === 'yellow', // predicate
        ({ color }) => color, // ifTrue
        ({ color }) => color.length // orElse
    )
)
.subscribe(value => console.log(value));

• The output will be: "yellow" and then will be print "6"

switchMap

switchMapIfFalse

• Could be usefully if your predicate are false on switch observables

of({ color: 'yellow' }, { color: 'red' }).pipe(
    switchMapIfFalse(
        ({ color }) => color === 'yellow', // predicate
        ({ color }) => of(color) // ifFalse -> Observable('red')
    )
)
.subscribe(value => console.log(value));

• The output will be: "red"

switchMapIfTrue

• Could be usefully if your predicate are true on switch observables

of({ color: 'yellow' }, { color: 'red' }).pipe(
    switchMapIfTrue(
        ({ color }) => color === 'yellow', // predicate
        ({ color }) => of(color) // ifTrue -> Observable('yellow')
    )
)
.subscribe(value => console.log(value));

• The output will be: "yellow"

switchMapIfOrElse

• Could be usefully when you need that two action bases on same predicate,similar of if/else, but for this case, in the Observable context, example:

of({ color: 'yellow' }, { color: 'red' }).pipe(
    switchMapIfOrElse(
        ({ color }) => color === 'yellow', // predicate
        ({ color }) => of(color), // ifTrue -> Observable("yellow")
        ({ color }) => of(color.length) // orElse -> Observable(6)
    )
)
.subscribe(value => console.log(value));

• The output will be: "yellow" and then will be print "3"

tap

tapIfFalse

• Will be tap when the predicate are false

of({ color: 'yellow' }, { color: 'red' }).pipe(
    tapIfFalse(
        ({ color }) => color === 'yellow', // predicate
        ({ color }) => console.log(color), // ifFalse -> ("red")
    )
)
.subscribe();

• The output will be: "red"

tapIfTrue

of({ color: 'yellow' }, { color: 'red' }).pipe(
    tapIfTrue(
        ({ color }) => color === 'yellow', // predicate
        ({ color }) => console.log(color), // ifTrue
    )
)
.subscribe();

• First output: "yellow"

tapIfOrElse

• Could be usefully when you need that two action bases on the same predicate,similar of if/else, but for this case, in the Observable context, example:

of({ color: 'yellow' }, { color: 'red' }).pipe(
    tapIfOrElse(
        ({ color }) => color === 'yellow', // predicate
        ({ color }) => console.log(color), // ifTrue 
        ({ color }) => console.log(color.length) // orElse
    )
)
.subscribe();

• First output: "yellow"
• Second output: "3" because the length of red is 3.