wait-until  

This simple Node.js module provides a way to check for a condition every so
often, then run a callback after the condition is met or the allotted time
expires.

This is good if you need to wait for specific state changes in code that you
don't have direct control over, like a headless web browser.

Usage

``js
var waitUntil = require('wait-until');

waitUntil(interval, times, function condition() {
return (someCondition ? true : false);
}, function done(result) {
// result is true on success or false if the condition was never met
});
`

The condition function will be called up to times times, starting after
interval milliseconds. Once it returns true (or a truthy value), the
done callback will be called with result equal to true (or whatever value
the condition function returned).

If the condition is never met within the specified timeframe, done will be
called with result equal to false (or whatever falsy value the condition
function returned the last time it was called).

$3

Don't want to remember the order of arguments? Then use the
fluent interface:

`js
var waitUntil = require('wait-until');

waitUntil()
.interval(500)
.times(10)
.condition(function() {
return (someCondition ? true : false);
})
.done(function(result) {
// do stuff
});
`

$3

If the condition function accepts an argument, then it is assumed to be a
callback function which will be called with the result of the test:

`js
var waitUntil = require('wait-until');

waitUntil()
.interval(500)
.times(10)
.condition(function(cb) {
process.nextTick(function() {
cb(someCondition ? true : false);
});
})
.done(function(result) {
// do stuff
});
`

$3

You can specify .times(Infinity)` if you like, but it's probably better to set
and enforce a reasonable timeout.