Another promise limiter (adding concurrency to promises). This library uses rxjs to control concurrency, it also adds a little bit of extra functionality around how you get the results.
To install this package, run,
npm install --save promax
Once it's installed, you can use Promax to run your promises with a specified concurrency value. Pretend we had the following promise function:
function createPromiseFunction ( returns = null , timeout = 0 ) {
return new Promise ( resolve => {
setTimeout ( ( ) => {
resolve ( returns ) ;
} , timeout ) ;
} ) ;
}
Our code with Promax could be used in many ways:
import { Promax } from ' promax ' ;
async function run ( ) {
const limit = 2 ;
const expectedValues = [ 1 , 2 , 3 ] ;
const promax = Promax . create ( limit ) . add (
expectedValues . map ( ev => ( ) => createPromiseFunction ( ev ) )
) ;
const results = await promax . run ( ) ;
const resultMap = promax . getResultMap ( ) ;
}
NOTE: In this case, we didn't change the settings at the start so if a promise is rejected, it'll throw and end the call.
What if we don't want it do throw?
import { Promax } from ' promax ' ;
async function run ( ) {
const limit = 2 ;
const expectedValues = [ 1 , 2 , 3 ] ;
const promax = Promax . create ( limit , { throws : false } ) . add (
expectedValues . map ( ev => ( ) => createPromiseFunction ( ev ) )
) ;
}
When it doesn't throw, it wraps errored results in an ErrorResult instance. Using insanceof ErrorResult will tell you whether or not there was an error in your array of results. Let's assume we have the following function,
function createFailedPromiseFunction ( returns = 0 , timeout = 0 ) {
return new Promise ( ( resolve , reject ) => {
setTimeout ( ( ) => {
reject ( returns ) ;
} , timeout ) ;
} ) ;
}
Then we may get the following,
import { Promax } from ' promax ' ;
async function run ( ) {
const limit = 2 ;
const promax = Promax . create ( limit , { throws : false } ) . add ( [
( ) => createPromiseFunction ( 1 ) ,
( ) => createFailedPromiseFunction ( 2 ) ,
( ) => createPromiseFunction ( 3 ) ,
] ) ;
const results = await promax . run ( ) ;
const resultMap = promax . getResultMap ( ) ;
}
IMPORTANT: If you don't need the functionality above, you can chain everything into one call:
import { Promax } from ' promax ' ;
async function run ( ) {
const limit = 2 ;
const expectedValues = [ 1 , 2 , 3 ] ;
const results = Promax . create ( limit ) . add (
expectedValues . map ( ev => ( ) => createPromiseFunction ( ev ) )
) . run ( ) ;
}
And you can send in the result map by reference:
import { Promax } from ' promax ' ;
async function run ( ) {
const limit = 2 ;
const expectedValues = [ 1 , 2 , 3 ] ;
const resultMap = { valid : [ ] , error : [ ] } ;
const results = Promax . create ( limit )
. setResultMapOutput ( resultMap )
. add (
expectedValues . map ( ev => ( ) => createPromiseFunction ( ev ) )
) . run ( ) ;
}
