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cdax/async_promise.js

Last active August 29, 2015 14:10
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A promise-style asynchronous function in Node
Raw
async_promise.js
var http = require('http');
var Q = require('q');
var download = function(url) {
var page = '';
var deferred = Q.defer();
http.get(url, function(res) {
var page_size = res.headers['content-length'] || res.headers['Content-Length'];
res.on('data', function(chunk) {
page += chunk.toString();
//As an upside of using promises, we also get to track download progress using deferred.notify()
deferred.notify(100 * page.length / page_size);
});
res.on('end', function() {
//Promise fullfilled
deferred.resolve(page);
});
res.on('error', function(err) {
//Promise rejected
deferred.reject(err);
});
});
return deferred.promise;
};
//Calling download
downlaod('http://nodejs.org')
.then(function(page) {
console.log('Downloaded.');
}, function(err) {
console.log(err);
}, function(progress) {
console.log('Downloading... (' + progress + '%)');
});
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