simple_twitter.user.js

// ==UserScript==
// @name           simple twitter
// @namespace      http://www.hatena.ne.jp/hitode909/
// @description    make posts simple.
// @include        http://twitter.com/*
// @require        http://code.jquery.com/jquery-latest.js
// ==/UserScript==

(function(){
    $('li.status').each(function(){
        // originalContentは初期状態のHTML
        this.content = $('span.entry-content', $(this));
        this.originalContent = this.content.html();
        // contentからreply,anchor切り出す
        // textは形態素解析の本文になる部分
        var replyExp = /@\<a href=\"\/\w+\"\>\w+\<\/a\>\s?/g;
        this.replyTo = (this.originalContent.match(replyExp) || []).join(' ');
        this.content.html(this.content.html().replace(replyExp,''));
        this.anchors = $('a',this.content).remove();
        this.text = this.content.text();

        this.verbs = [];
        this.verbMode = false;
        this.toggleView = function() {
            this.verbMode = !this.verbMode;
            if (this.verbMode) {
                this.content.html( this.replyTo + this.verbs.join('')
                           ).append(this.anchors);
            } else {
                this.content.html(this.originalContent);
            }
        };
        $(this).click(this.toggleView);
        this.content.empty().append($(document.createElement('img')).attr('src', 'http://static.twitter.com/images/ajax.gif'));

        // JSON取得
        var self = this;
        GM_xmlhttpRequest({
            method: "GET",
            url: 'http://mimitako.net/api/mecapi.cgi?'+$.param({sentence:this.text, format:'json', response:'surface,feature'}),
            onload: function(response) {
                var mecab;
                try {
                    mecab = eval(response.responseText);
                } catch(e) {
                    self.verbs = 'Failed to receive data.';
                    return;
                };
                self.verbs = [];
                $.each(mecab, function(){
                    // それっぽいものだけ取り出す
                    var features = this.feature.split(',');
                    if (features[0] == '動詞' ||
                        (features[0] == '名詞' && ['一般', '固有名詞'].indexOf(features[1]) != -1)) {
                        if (features[6] == '*'){
                            self.verbs.push(this.surface);
                        } else {
                            self.verbs.push(features[6]);
                        }
                    }
                });
                self.verbs = $.unique(self.verbs);
                self.toggleView();
            }
        });
    });
})(jQuery);

What exactly does this script do?