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<title>Getting a Script Node with JSON Data</title>
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<h1>Getting a Script Node with JSON Data</h1>
<div class="exampleIntro">
<p>This example employs the <a href="http://developer.yahoo.com/yui/3/get/">YUI
Get Utility</a> in a simple use case: retrieving JSON data from a cross-domain
web service. While this is a relatively common usage, it's important to
understand the security ramifications of this technique. Scripts loaded via the
Get Utility (or any other "script node" solution) execute immediately
once they are loaded. If you do not fully control (or fully trust) the script's
source, this is not a safe technique and it can put the security of your users'
data at risk. (For more information on the dangers of cross-site scripting
[XSS] exploits, <a
href="http://en.wikipedia.org/wiki/Cross-site_scripting">check out the
Wikipedia entry on this subject</a>.)</p> <p>Here, we will use a trusted Yahoo!
Search web service called <a
href="http://developer.yahoo.com/search/siteexplorer/V1/inlinkData.html">Site
Explorer</a> to return a list of inbound links for a given URL. The principal
difference between this example and similar examples using <a
href="http://developer.yahoo.com/yui/3/io/">YUI IO Utility</a> is
that this technique does not require a server-side proxy. The browser connects
directly to the third-party web service without bouncing through a proxy page
as is required when using the XMLHttpRequest object (on which IO Utility
relies).</p>
</div>
<!--BEGIN SOURCE CODE FOR EXAMPLE =============================== -->
<div id="container">
<!--Use a real form that works without JavaScript:-->
<form method="GET" action="http://siteexplorer.search.yahoo.com/advsearch" id="siteExplorer">
<label for="searchString">Site URL:</label> <input type="text" name="p" id="searchString" value="http://developer.yahoo.com/yui" size="40">
<input type="hidden" name="bwm" value="i">
<input type="hidden" name="bwms" value="p">
<input type="submit" id="siteExplorerData" value="Click here to get JSON data.">
</form>
<div id="results">
<!--JSON output will be written to the DOM here-->
</div>
</div>
<script type="text/javascript">
YUI({base:"../../build/", timeout: 10000, filter:"debug", logInclude: {get:true, event:true, example:true}}).use("node", "dump",
function(Y) {
// We are going to create a global variable to get the
// data back from the web service
MyNamespace = YUI.namespace('example.SiteExplorer');
var elResults = Y.one("#results"),
tIds = {},
loading = false,
current = null;
// We use the Get Utility's success handler in conjunction with
// the web service callback in order to detect bad responses
// from the web service.
var onSiteExplorerSuccess = function(o) {
// stop blocking requests
loading = false;
// A success response means the script node is inserted. However, the
// utility is unable to detect whether or not the content of the script
// node is correct, or even if there was a bad response (like a 404
// error). To get around this, we use the web service callback to
// verify that the script contents was correct.
if (o.tId in tIds) {
Y.log("The Get Utility has fired the success handler indicating that the " +
"requested script has loaded and is ready for use.", "info", "example");
} else {
Y.log("The Get utility has fired onSuccess but the webservice callback did not " +
"fire. We could retry the transaction here, or notify the user of the " +
"failure.", "info", "example");
}
};
var onSiteExplorerFailure = function(o) {
Y.log("The Get Utility failed.", "info", "example");
};
var onSiteExplorerTimeout = function(o) {
Y.log("The Get Utility timed out.", "info", "example");
};
//function to retrieve data from Yahoo! Site Explorer web service --
// http://developer.yahoo.com/search/siteexplorer/V1/inlinkData.html
var getSiteExplorerData = function() {
Y.log("Button clicked; getSiteExplorerData firing.", "info", "example");
// block multiple requests
if (loading) {
return;
}
loading = true;
//Load the transitional state of the results section:
elResults.set("innerHTML", "<h3>Retrieving incoming links for " +
Y.one("#searchString").get('value') + ":</h3>" +
"<img src='http://l.yimg.com/a/i/nt/ic/ut/bsc/busybar_1.gif' " +
"alt='Please wait...'>");
//prepare the URL for the Yahoo Site Explorer API:
var sURL = "http://search.yahooapis.com/SiteExplorerService/V1/inlinkData?" +
"appid=3wEDxLHV34HvAU2lMnI51S4Qra5m.baugqoSv4gcRllqqVZm3UrMDZWToMivf5BJ3Mom" +
"&results=20&output=json&omit_inlinks=domain" +
"&callback=MyNamespace.callback" +
"&query=" + encodeURIComponent(Y.one("#searchString").get('value'));
//This simple line is the call to the Get Utility; we pass
//in the URL and the configuration object, which in this case
//consists merely of our success and failure callbacks:
var transactionObj = Y.Get.script(sURL, {
onSuccess: onSiteExplorerSuccess,
onFailure: onSiteExplorerFailure,
onTimeout: onSiteExplorerTimeout,
timeout: 20000,
context: Y
});
//The script method returns a single-field object containing the
//tranaction id:
Y.log("Get Utility transaction started; transaction object: " + Y.dump(transactionObj), "info", "example");
// keep track of the current transaction id. The transaction will be
// considered complete only if the web service callback is executed.
current = transactionObj.tId;
};
MyNamespace.callback = function(results) {
Y.log("Web service returned data to Y.example.SiteExplorer.callback; beginning to process.", "info", "example");
// Mark the transaction as complete. This will be checked by the onSuccess
// handler to determine if the transaction really succeeded.
tIds[current] = true;
//work with the returned data to extract meaningful fields:
var aResults = results.ResultSet.Result;
var totalLinks = results.ResultSet.totalResultsAvailable;
var returnedLinkCount = results.ResultSet.totalResultsReturned;
if(aResults) {//there are inbound links; process and display them:
//write header and open list of inbound links:
var html = "<h3>There are " +
totalLinks +
" inbound links for this page; here are the first " +
returnedLinkCount +
":</h3><ol>";
//process list of inbound links:
for (var i=0; i < aResults.length; i++) {
html += "<li><strong>" +
aResults[i].Title +
":</strong> <a href='" +
aResults[i].Url +
"'>" + aResults[i].Url +
"</a></li>";
}
//close list of inbound links
html += "</ol>";
} else {//no inbound links exist for this page:
var html = "<h3>There are no inbound links for the page specified.</h3>";
}
//insert string into DOM:
elResults.set('innerHTML', html);
};
//suppress default form behavior
Y.on("submit", function(e) {
e.preventDefault();
getSiteExplorerData();
}, "#siteExplorer");
});
</script>
<!--END SOURCE CODE FOR EXAMPLE =============================== -->
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