README.md

Reproduces RxJs behavior

There is no generic operators as in RxJs yet, but the main idea behind is presented here...

mimic-RxJS.js

function map(transformFn) {
    return createObservable( outputObserver => {
        this.subscribe({
            next: x => {
                const y = transformFn(x)
                outputObserver.next(y)
            },
            error: e => outputObserver.error(e),
            complete: () => outputObserver.complete
        })
    })
}

function filter(filterFn) {
    return createObservable( outputObserver => {
        this.subscribe({
            next: x => {
                if (filterFn(x)) outputObserver.next(x)
            },
            error: e => outputObserver.error(e),
            complete: () => outputObserver.complete
        })
    })
}

function delay(timeout) {
    return createObservable( outputObserver => {
        this.subscribe({
            next: x => {
                setTimeout(() => {
                    outputObserver.next(x)
                }, timeout);
            },
            error: e => outputObserver.error(e),
            complete: () => outputObserver.complete
        })
    })
}

const createObservable = subscribe => {
    return { subscribe, map, filter, delay }
}

// =============================================================
// Testing
// =============================================================

// One of our own observable (1st)
const arrayObservable = createObservable( observer => {
    [10, 20, 30].forEach( observer.next )
    observer.complete()
})

// One of our own observable (2nd)
const clickObservable = createObservable( observer => {
    document.addEventListener('click', observer.next)
})

// Our own observer
const observer = {
    next    : (data) => console.log(data),
    error   : (data) => console.error(data),
    complete: ()     => console.info('done')
}

// Do the subscriptions

arrayObservable
    .map( x => x/10 )
    .filter( x => x != 2 )
    .subscribe(observer)

clickObservable
    .map( ev => ev.clientX )
    .filter( x => x<200 )
    .delay(500)
    .subscribe(observer)