dedup-async

Deduplicate concurrent promise calls by resolving them together.

dedup-async wraps any function that returns promise. Succeeding call to the same function will get a promise that resolves/rejects along with the previous pending promise if any, but not triggering the actual logic.

const dedupa = require('dedup-async')
 
let evil
let n = 0
 
function task() {
    return new Promise((resolve, reject) => {
        if (evil)
            throw 'Duplicated concurrent call!'
        evil = true
    
        setTimeout(() => {
            console.log('Working...')
            evil = false
            resolve(n++)
        }, 100)
    })
}
 
function test() {
    dedupa(task)
        .then (d => console.log('Finish:', d))
        .catch(e => console.log('Error:', e))
}
 
test()                //Prints 'Working...', resolves 0
test()                //No print,            resolves 0
setTimeout(test, 200) //Prints 'Working...', resolves 1