startWith

First emit given values to sinks.

1linkfunction startWith<A, T>(...initial: A[]): (src: Source<T>) => Source<A | T>

1link​import { interval, startWith, map, take, subscribe, pipe } from 'callbag-common';

2link​

3link​pipe(

4link​  interval(1000),

5link​  map(i => 3 - i),

6link​  take(3),

7link​  startWith('Ready?'),

8link​  subscribe(console.log),

9link​)

 Ready?
 3
 2
 1

👉 startWith() is useful for pre-populating streams that depend on some external event for their emissions. For example, your stream might be dependent on user clicking a button, but you would want it to have some initial value:

1linkpipe(

2link  fromEvent(btn, 'click'),

3link  scan(c => ++c, 0),

4link  startWith(0),                                 // --> without this, the message will only be displayed after first click

5link  subscribe(c =>

6link    res.textContent = `You have clicked ${c} times!`

7link  )

8link)

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