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Node.js: Expanding Shortened URLs

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Node.js: Expanding Shortened URLs

· Web Dev Zone ·
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This blog post explains how one can use Node.js to expand a URL that has been shortened by a service such as t.co (built into Twitter) and bit.ly. We’ll look at a simple implementation and at an advanced implementation that uses promises.

 

The minimum

You need to install Mikeal Rogers’ request module:

npm install request

That module automatically follows all redirects from the shortened URL. Once you are at your final destination, you only need to find out where you are:

var request = require("request");

function expandUrl(shortUrl) {
    request( { method: "HEAD", url: shortUrl, followAllRedirects: true },
        function (error, response) {
            console.log(response.request.href);
        });
}

Prettier with promises

If you want to write a function that returns the expanded URL, more work is needed. You have the option of using a callback, but promises usually lead to prettier code. Let’s use Kris Kowal’s Q module:

npm install q

The “promising” code looks as follows.

var Q = require("q");
var request = require("request");

function expandUrl(shortUrl) {
    var deferred = Q.defer();
    request( { method: "HEAD", url: shortUrl, followAllRedirects: true },
        function (error, response) {
            if (error) {
                deferred.reject(new Error(error));
            } else {
                deferred.resolve(response.request.href);
            }
        });
    return deferred.promise;
}

Invoking the function works like this: 

expandUrl("http://example.com")
.then(function (longUrl) {
    console.log(longUrl);
});

 

Deploying code to production can be filled with uncertainty. Reduce the risks, and deploy earlier and more often. Download this free guide to learn more. Brought to you in partnership with Rollbar.

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