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speedns.js
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speedns.js
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/**
* Static class that holds all the utility functions.
*/
var SpeedNS = {
/**
* Regular expression to match a domain name from uri.
*/
domainRegex: /((http)|(https)):\/\/[A-Za-z0-9.\-]+\//,
/**
* Fires DNS lookups for all the links in the current document.
*
* @param {object} e is the current html document for which the onload event
* has fired.
*/
prefetch: function() {
var doc = document,
links = doc.getElementsByTagName("a");
var uniqueLinks = {}, i, l;
for (i = 0, l = links.length; i < l; i++ ) {
var uri = links[i].href,
matches = SpeedNS.domainRegex.exec(uri),
domain = matches[0];
// hash each domain name.
uniqueLinks[domain] = false;
}
for (var ud in uniqueLinks) {
/**
* We do it only if its a property that is created on object, because
* some libraries like prototype can screw this up.
*/
if (uniqueLinks.hasOwnProperty(ud)) {
SpeedNS.prefetchDNSForDomain(ud,
SpeedNS.processHeadResponses);
}
}
},
/**
* Prefetches DNS for the domain using hidden image technique. Uses the
* favicon image as source.
*
* @param {String} domain is the domain for which the DNS should be
* prefetched.
*/
prefetchDNSForDomain: function(domain) {
// some browsers do not support image object, so check if it does.
if (document.images) {
var i = new Image(16, 16);
i.src = domain + "favicon.ico";
}
}
};
// Alias it on YUI instance.
Y.speedns = SpeedNS;