otherlib

Yet another javascript utility library

API Doc

• dedup
• delay
• retry
• throttle

dedup

Deduplicate concurrent generation of the same promise task. If there's an ongoing pending promise, succeeding calls to the same promise-generator function resolves/rejects along with the pending promise.

Deduplicate concurrent promise calls by resolving them together.

dedup 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 does not trigger 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. (Starts a new pending promise)
test()                //No print,            resolves 0. (Resolves together with the previous promise)
test()                //No print,            resolves 0. (Resolves together with the previous promise)
setTimeout(test, 200) //Prints 'Working...', resolves 1. (Starts a new pending promise since the previous one has completed)

delay

Wrap the provided data/function/promise in a delayed a promise.

await delay(1000)
await delay(1000, 'the result to be resolved')
await delay(1000, a_func)

retry

Retry the specific task conditionally

(function() {
    let n = 0
    let task = () => {
        return new Promise((resolve, reject) => {
            if (++n > 2)
                resolve(n)
            else
                reject('Something wrong: ' + n)
        })
    }
    return retry(task, {
        filter: err => true,		//retry with any error
        retry: 5,			//max retry attempt
        intervalMs: 50,			//wait before retry 
        timeoutMs: 0,			//total timeout limit. 0 indicates no total timeout			
        log: console.log,		//optionally, log the details
        name: 'test',			//name shown in log
    })
})().then(console.log).catch(console.error)

throttle

Wrap an async function with throttle control, to control the speed of execution.

const throttle = require('otherlib/throttle')

let task(n) {
	return new Promise(resolve => {
		console.log('start', n)
		setTimeout(() => {
			console.log('done', n)
			resolve()
		}, 1000)
	})
}

let options = {
	concurrency: 10,	// Max allowed concurrent calls of the target function
}
let throttledTask = throttle(task, options)

let tasks = []
for (let i = 0; i < 30; i++)
	tasks.push(throttledTask(i))

Promise.all(tasks)
	.then(() => console.log('complete'))

file-cache

A file based map object for caching, e.g. local auth session for CLI.

const FileCache = require('otherlib/file-cache.js')
const cache = FileCache('my-file.json')
cache.put('k1', 'v1')
cache.get('k1) === 'v1'	//true
cache.keys()	//['k1']
cache.remove('k1')
cache.clear()