changed
Polls HTTP resources and fires events when they change.
Features
- Supports HTTP and HTTPS
- Transparently decodes gzipped resources
Installation
npm install robinjmurphy/changed
Usage
var changed = require('changed-http');
var resource = new changed.Resource('http://www.example.com');
resource.on('changed', function (current, previous) {
console.log('Resource changed. Response body was ' + previous + ' , is now ' + current + '.');
});
resource.startPolling(5000);
API
new changed.Resource(url, options)
Parameters
url
- stringoptions
- object - configuration options
Options
The options
object supports all of the standard options from http.request and https.request. In addition, it supports the following properties:
compare
- function - overrides the default response body comparison. Receives the current response body as its first argument and the previous response body as its second argument. Should return true
if the responses differ.
.startPolling(interval)
Start polling the resource for changes.
Parameters
interval
- number - the interval time in milliseconds (default 10000
)
.stopPolling()
Stop polling the resource.
Events
changed
Fired when the resource's body changes.
resource.on('changed', function (current, previous) {
});
error
Fired when an error occurs.
resource.on('error', function (error) {
});
response
Fired each time a response is received whilst polling.
resource.on('response', function (body, res) {
});
Logging
All polling requests are logged using console.info
by default. To use a custom logger, like Winston, just set the changed.logger
property:
var changed = require('changed-http');
var winston = require('winston');
changed.logger = winston;
Examples
Custom response comparison
In the following example the changed
event is only fired when the foo
property in a JSON response changes.
var changed = require('changed-http');
var resource = new changed.Resource('http://www.example.com/some/json/file.json', {
compare: function (current, previous) {
var currentJson = JSON.parse(current);
var previousJson = JSON.parse(previous);
return (currentJson.foo !== previousJson.foo);
}
});
resource.startPolling(5000);