7.5 KiB
Description
Erre is a modern, performant and tiny (~0.5kb minified) streams script using generators that runs on modern browsers and node. It can be used to manage any kind of sync and async event series and it's inspired to bigger libraries like:
Installation
npm i erre -S
Usage
You can use it to create and manipulate simple event streams
import erre from 'erre'
const stream = erre(
string => string.toUpperCase(),
string => [...string].reverse().join('')
)
stream.on.value(console.log) // EVOL, ETAH
stream.push('love')
stream.push(async () => await 'hate') // async values
It supports async and sync event chains thanks to ruit
const userNamesStream = erre(
async user => await patchUsers(user), // async function returning a users collection
users => users.map(user => user.name)
)
userNamesStream.on.value(console.log) // ['John'...]
userNamesStream.push({
name: 'John',
role: 'Doctor',
age: 24
})
API
erre(...functions)
@returns stream
Create an erre stream object.
The initial functions list is optional and it represents the chain of async or sync events needed to generate the final stream output received via on.value callbacks
stream
It's an enhanced Generator object having additional API methods
stream.push(value)
@returns stream
Push a new value into the stream that will be asynchronously modified and returned as argument to stream.on.value method
Example
const stream = erre()
stream.on.value(console.log) // 1
stream.push(1)
stream.on.value(callback)
@returns stream
Add a callback that will be called receiving the output of the stream asynchronously
Example
const stream = erre(val => val + 1)
stream.on.value(console.log) // 2
stream.on.value(val => console.log(val * 2)) // 4
stream.push(1)
stream.on.error(callback)
@returns stream
Add a callback that will be called in case of errors or promise rejections during the output generation
Example
const stream = erre(val => {
throw 'error'
})
stream.on.value(console.log) // never called!!
stream.on.error(console.log) // 'error'
stream.push(1)
stream.on.end(callback)
@returns stream
Add a callback that will be called when the stream will be ended
Example
const stream = erre()
stream.on.end(() => console.log('ended!')) // ended!
stream.end()
stream.off.value(callback)
@returns stream
@throws Error if callback isn't registered
Removes a previously-registered callback
Example
const stream = erre()
const handler = (value) => console.log('handling', value)
stream.on.value(handler)
stream.push(1) // handler called, logs: handling 1
stream.off.value(handler)
stream.push(2) // handler is not called
// throws, because the handler is not registered
const someOtherHandler = () => console.log(`don't register me`)
stream.off.value(someOtherHandler)
stream.off.error(callback)
@returns stream
@throws Error if callback isn't registered
stream.off.end(callback)
@returns stream
@throws Error if callback isn't registered
stream.connect(function)
@returns stream
Enhance the stream adding a new operation to the functions chain to generate its output
Example
const stream = erre(val => val + 1)
stream.on.value(console.log) // 2, 4
stream.push(1)
// enhance the stream
stream.connect(val => val * 2)
stream.push(1)
stream.end()
@returns stream
End the stream
Example
const stream = erre(val => val + 1)
stream.on.value(console.log) // 2
stream.push(1)
// end the stream
stream.end()
// no more events
stream.push(1)
stream.push(1)
stream.push(1)
stream.fork()
@returns new stream object
Create a new stream object inheriting the function chain from its parent
Example
const stream = erre(val => val + 1)
stream.on.value(console.log) // 2, 3
stream.push(1)
const fork = stream.fork()
fork.on.value(console.log)
fork.connect(val => val * 10) // 20, 60
// 2 independent streams
fork.push(1)
stream.push(2)
fork.push(5)
stream.next(value)
@returns { done: true|false, value: Promise|undefined }
Run a single stream sequence (without dispatching any event) returning as value a promise result of the stream computation.
If the stream was ended the done value will be true and the value will be undefined.
Example
const stream = erre(val => val + 1)
stream.on.value(console.log) // never called
const { value } = stream.next(1)
value.then(console.log) // 2
erre.cancel()
Static function that if returned by any of the stream functions chain can be used to filter or stop the computation
Example
const stream = erre(val => {
if (typeof val !== 'number') return erre.cancel()
return val + 1
})
stream.on.value(console.log) // 2, 3
stream.push(1)
stream.push('foo') // filtered
stream.push('1') // filtered
stream.push(2)
erre.off()
Static function that if returned by any of the subscribed callbacks can be used to unsubscribe it
Example
const stream = erre(val => val + 1)
stream.on.value(val => {
// if this condition will be matched, this callback will be unsubscribed
if (typeof val !== 'number') return erre.off()
console.log(val)
}) // 2
stream.push(1)
// this value will let the previous listener unsubscribe itself
stream.push('foo')
stream.push('1')
// this value will not be logged because the stream.on.value was unsubscribed
stream.push(2)
erre.install(name, fn)
@returns erre
Extend erre adding custom API methods. Any plugin must have at lease a name (as string) and a function
Example
// alias the `console.log` with `erre.log`
erre.install('log', console.log)
const stream = erre(val => val + 1)
stream.on.value(erre.log) // 2, 3
stream.push(1)
stream.push(2)
TODO List
- erre.fromDOM - to stream DOM nodes events
- erre.merge - to merge multiple stream results into one