Install

$ npm install js-streams

Import

let js_stream = require('js-streams')

Optional

An object that wrapped a single value and provides checks to validate it's presence.

#isPresent()

Check if the value is present.

js_stream.Optional.empty().isPresent() // false
js_stream.Optional.forValue(undefined).isPresent() // false
js_stream.Optional.forValue(5).isPresent() // true
js_stream.Optional.forValue(null).isPresent() // false
js_stream.Optional.forNullableValue(null).isPresent() // true

#get()

Get the wrapped value. Throws an exception if isPresent() returns False.

js_stream.Optional.empty().get() // throws Error
js_stream.Optional.forValue(5).get() // 5
js_stream.Optional.forValue(js_stream.Optional.forValue(5)).get() // 5

#ifPresent(function, function)

A method to consume the internal value if it is present.

js_stream.Optional
    .forValue(5)
    .ifPresent(
        function(value) {
            // value is 5
        }
    )

Seconds callback is invoked when the value is not present.

js_stream.Optional
    .forValue(5)
    .ifPresent(
        null,
        function() {
            // no value present
        }
    )

Stream

A wrapper for either an array or single value. Has method for filtering and finding values using Optional values as return value.

Create a stream

js_stream.Stream.forValue().get() // []
js_stream.Stream.forValue(1).get() // [1]
js_stream.Stream.forValue([1, 2, 3]).get() // [1, 2, 3]

Create a stream

js_stream.Stream.forValue().get() // []
js_stream.Stream.forValue(1).get() // [1]
js_stream.Stream.forValue([1, 2, 3]).get() // [1, 2, 3]

#isEmpty()

js_stream.Stream.forValue().isEmpty() // true
js_stream.Stream.forValue(1).isEmpty() // false

#filter()

Filter the contents of the stream using a predicate function and returns a new stream with the results.

js_stream.Stream.forValue([1, 2]).filter( function(v){return v==2}).get() // [2]

#first()

Returns an Optional value of the first entry in the stream or an empty Optional if the stream was empty.

js_stream.Stream.forValue([1, 2]).first().isPresent() // true
js_stream.Stream.forValue([1, 2]).first().get() // 1
js_stream.Stream.forValue([]).first().isPresent() // false

#find()

Returns an Optional value of the first match found for the supplied predicate.

js_stream.Stream.forValue([1, 2])
    .find(
        function(v){ return v==2 }
        )
    .isPresent() // true

js_stream.Stream.forValue([1, 2])
    .find(
        function(v){ return v==2; }
        )
    .get() // 2

js_stream.Stream.forValue([1])
    .find(
        function(v){return v==2}
    )
    .isPresent() // false

#map()

Calls a defined callback function on each element of an stream, and returns an Stream that contains the results.

js_stream.Stream.forValue([1, 2])
    .map(
        function(v){ return v*2 }
        )
    .get() // [2, 4]

#forEach()

Calls a defined callback function on each element of the stream.

js_stream.Stream.forValue([1, 2])
    .forEach(
        function(v){ // do something }
    )