stoppable.js

Utility library implementing tooling to make stoppable functions...

This library enables the user to drop out of a function/generator without the need to thread the result through the call stack. This is in concept similar to executing return .. from a nested loop to terminate and return from a function but stoppable.js allows us to do the same from a nested set of function calls. This is also similar to Python's raise StopIteration approach to stopping iteration.

• stoppable.js
  • Install / import
  • Components
    • stoppable(..)
    • stoppable.STOP / stoppable.STOP(..)
  • Examples
    • Function
    • Async function
    • Generator
    • Async generator
  • License

Install / import

$ npm install --save ig-stoppable

var stoppable = require('ig-stoppable')

Components

stoppable(..)

Create a wrapper for the input function/generator.

stoppable(<function>)
    -> <function>

stoppable(<async-function>)
    -> <async-function>

stoppable(<generator>)
    -> <generator>

stoppable(<async-generator>)
    -> <async-generator>

stoppable.STOP / stoppable.STOP(..)

A special object/constructor that can either be returned/thrown as-is or used to create an instance to be returned thrown.

stoppable.STOP

stoppable.STOP()
stoppable.STOP(<value>)
    -> <stop-object>

This will get intercepted by stoppable(..) and appropriately handled, stopping the function iterator and merging the value into the yields of a generator or returning it from a function depending on the wrapper type.

<stop-object> can contain a value that will get handled by stoppable(..) (default: undefined).

Examples

Function

var func = stoppable(function(){
    // ...

    throw stoppable.STOP('something')

    // ...
})

var value = func() // -> 'something'

Dropping out of recursion avoiding threading the result up the chain:

// Note that we split the recursive part and the interface part, this is done
// to keep the STOP catching only to the top level and thus avoid threading 
// the result back up the recursion...
var _find = function(L, e){
    if(L.length == 0){
        throw stoppable.STOP(false) }
    if(L[0] == e){
        throw stoppable.STOP(true) }
    // look further down...
    _find(L.slice(1), e) }

var find = stoppable(_find)

find([1,2,3,4,5,6,7], 6) // -> true

For more examples see type.js' Array.prototype.smap(..) and friends.

Async function

var func = stoppable(async function(){
    // ...

    throw stoppable.STOP('something')

    // ...
})

var value = await func() // -> 'something'

Generator

var gen = stoppable(function*(){
    // ...

    throw stoppable.STOP('something')

    // ...
})

var value = [...gen()] // -> ['somthing']

Async generator

var agen = stoppable(async function*(){
    // ...

    throw stoppable.STOP('something')

    // ...
})

var value = awat agen() // -> ['something']

License

BSD 3-Clause License

Copyright (c) 2022-, Alex A. Naanou,
All rights reserved.