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README.md
@joepie91/promise-delay-every
A function for writing one per N amount of time rate-limiting implementations.
When called, it returns a 'delayer' function. This delayer function can be called repeatedly; every time it is called, it returns a Promise that resolves delay
milliseconds further into the future. The first time it is called, it resolves immediately.
So for example, if you specify a delay
of 2000 milliseconds, the Promise returned from the first call will resolve immediately; the Promise returned from the second call will resolve after 2 seconds, the Promise resolved from the third call will resolve after 4 seconds, and so on.
All of these times are relative to the first call you make - so in the above example, there are 2 seconds between every resolution:
0ms Call 1
0ms Resolve 1
2ms Call 2
3ms Call 3
5ms Call 4
2000ms Resolve 2
4000ms Resolve 3
6000ms Resolve 4
If you wait longer than the delay to call the delayer function again, the returned Promise will resolve immediately and that time becomes the new base time for future delays:
0ms Call 1
0ms Resolve 1
2ms Call 2
2000ms Resolve 2
... time passes, beyond the 2000ms delay ...
7400ms Call 3
7400ms Resolve 3
7402ms Call 4
9400ms Resolve 4
Example
See also example.js
for a runnable version. This example uses Bluebird for Promise.try
(read this article to understand why), but Bluebird is not required to use this module.
"use strict";
const Promise = require("bluebird");
const promiseDelayEvery = require("@joepie91/promise-delay-every");
let delayer = promiseDelayEvery(2000);
return Promise.try(() => {
return delayer();
}).then(() => {
// Logs immediately after running
console.log("Hello world 1");
return delayer();
}).then(() => {
// Logs 2 seconds after running
console.log("Hello world 2");
return delayer();
}).then(() => {
// Logs 4 seconds after running
console.log("Hello world 3");
});
API
promiseDelayEvery(delay)
Returns a new delayer
function.
- delay: The delay as a number, in millseconds.
delayer()
Returns a new Promise that will resolve at the next scheduled interval, according to the algorithm described at the top of this documentation.
The Promise will never reject.