@jcoreio/poll
v3.0.1
Published
handy promised-based polling API
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poll
yet another promise-based poller (I didn't like the API design of others out there)
Example
npm install --save @jcoreio/poll
const poll = require('@jcoreio/poll')
const superagent = require('superagent')
poll(() => superagent.get('http://google.com'), 1000)
.timeout(30000)
.then(() => console.log("You're connected to the internet!"))
poll(fn, interval, [options])
Begins calling fn
every interval
milliseconds until the condition passes
(which defaults to fn
didn't throw an Error
or return a rejected Promise
).
Returns a Promise
that resolves when polling finishes or fails, which may be:
- when
fn
calls thepass
method provided to it - when
fn
calls thefail
method provided to it - when
fn
returns/resolves to a value or throws/rejects with anError
that passes the condition - when a timeout is specified and
poll
times out waiting for any of the above
fn
will be called with a context object:
{
attemptNumber: number, // the number of this call (starting from 0)
elapsedTime: number, // the number of milliseconds since polling started
pass: (value: any) => void, // makes `poll` resolve immediately with this value
fail: (error: Error) => void, // makes `poll` reject immediately with this Error
}
You can change the condition by calling .until
on the returned Promise
:
poll(...).until((error, result) => result > 3)
error
will be the Error
from the last call to fn
(if it rejected or threw)
and result
will be the value it resolved to or returned otherwise.
You can specify a timeout (in milliseconds) by calling .timeout
on the returned Promise
:
poll(...).timeout(30000) // time out after 30 seconds
If you call .noWrapError()
on the returned Promise
, it won't wrap rejection errors.