tweetbuilder.js

function replace_links(tweet) {
    var pattern = /(http[s:\/a-zA-Z0-9\.\_]+)\b/gm;

    return tweet.replace(pattern, '<a href="$1">$1</a>');
}

function replace_mentions(tweet) {
    var pattern  = /(\@(.+?))\b/gm;
    var base_url = 'https://twitter.com/';

    return tweet.replace(pattern, '<a href="' + base_url + '$2">$1</a>');
}

function replace_hashtags(tweet) {
    var pattern  = /(\#(.+?))\b/gm;
    var base_url = 'https://twitter.com/hashtag/';

    return tweet.replace(pattern, '<a href="' + base_url + '$2">$1</a>');
}

/**
 * Build the tweet by parsing the hashtags, mentions, and the links
 * of the tweet.
 *
 * The order of precedence is quite specific only becase we don't want to
 * rereplace the links provided by the hashtag replacer and the mention replacer.
 *
 * Just make sure we replace the links before we replace everything else.
 *
 * @param  string  tweet
 * @return string
 */
function build_tweet(tweet) {
    return replace_mentions(replace_hashtags(replace_links(tweet)));
}

var sample_tweet = "@CrisisGroup again misses the point! We're tiered of hearing recycled stories meant to serve the hunter's story. https://t.co/TrWX9kWfos #HashTag @CrisisGroup #icg https://t.co/IAmAUrl";

console.log(build_tweet(sample_tweet));

// https://twitter.com/hashtag/tribezparty?src=hash
// ((\@.+?)\b|(\#.+?)\b|(http[s:\/a-zA-Z0-9\.\_]+)\b)