如何为豆瓣FM写一个chrome的歌词插件

对于喜欢豆瓣FM的同学来说，没有歌词是件令人苦恼的事，下面我就来总结下怎样为豆瓣FM写一个chrome的歌词插件。

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1.需要的技能

首先，你要会javascript，其次你要掌握一点chrome的hack，最后要有一个可以根据歌曲名查到歌词的API。

2.localStorage

localStorage与cookie类似，它是存储在客户端浏览器中的数据，它与cookie不同的一点是它没有时间限制。localStorage属于html5中的新特性。因为我们要做chrome的插件，所以按F12弹出开发者模式，点击resource，就可以看见localstorage选项了，通过localStorage，我们可以得到当前豆瓣播放的歌曲的id,歌曲名，演唱者等信息：

3.歌词迷的API

请求地址: http://geci.me/api/lyric/:song
返回格式: JSON
请求方法: GET
示例: 
curl 'http://geci.me/api/lyric/海阔天空'

{"count": 15,"code": 0,"result": [{ "aid": 2848529, "lrc": "http://s.geci.me/lrc/344/34435/3443588.lrc", "sid": 3443588, "artist_id": 2, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 2346662, "lrc": "http://s.geci.me/lrc/274/27442/2744281.lrc", "sid": 2744281, "artist_id": 2396, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 1889264, "lrc": "http://s.geci.me/lrc/210/21070/2107014.lrc", "sid": 2107014, "artist_id": 8715, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 2075717, "lrc": "http://s.geci.me/lrc/236/23651/2365157.lrc", "sid": 2365157, "artist_id": 8715, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 1563419, "lrc": "http://s.geci.me/lrc/166/16685/1668536.lrc", "sid": 1668536, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 1567586, "lrc": "http://s.geci.me/lrc/167/16739/1673997.lrc", "sid": 1673997, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 1571906, "lrc": "http://s.geci.me/lrc/167/16796/1679605.lrc", "sid": 1679605, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 1573814, "lrc": "http://s.geci.me/lrc/168/16819/1681961.lrc", "sid": 1681961, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 1656038, "lrc": "http://s.geci.me/lrc/179/17907/1790768.lrc", "sid": 1790768, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 1718741, "lrc": "http://s.geci.me/lrc/187/18757/1875769.lrc", "sid": 1875769, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 2003267, "lrc": "http://s.geci.me/lrc/226/22642/2264296.lrc", "sid": 2264296, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 2020610, "lrc": "http://s.geci.me/lrc/228/22889/2288967.lrc", "sid": 2288967, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 2051678, "lrc": "http://s.geci.me/lrc/233/23323/2332322.lrc", "sid": 2332322, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 2412704, "lrc": "http://s.geci.me/lrc/283/28376/2837689.lrc", "sid": 2837689, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" },{ "aid": 2607041, "lrc": "http://s.geci.me/lrc/311/31116/3111659.lrc", "sid": 3111659, "artist_id": 9208, "song": "\u6d77\u9614\u5929\u7a7a" }]
}

4.重头戏----javascript脚本

有了上面的准备工作，我们现在就可以安心的编码了。

首先，创建一个DoubanFM伪类（javascript中没有“真正的”类）

funciton DoubanFM() {this.name = '豆瓣FM';this.tmp_song_id = '';this.flag = 1;this.lyrics = this.draw_lyrics();
}

然后，对这个伪类拓展原型，创建新的函数:

【注】关于javascript拓展函数原型，我原来写过一篇博客：http://blog.csdn.net/wusuopubupt/article/details/14520209

用javascript创建新的节点（一个显示歌词的div,同时设置div的css）：

DoubanFM.prototype.draw_lyrics = funciton() {var lyrics_div = document.createElement('div');//用document.createElement()方法可以创造新的节点document.body.appendChild(lyrics_div);//用document.body.appendChild()方法把新的节点附加到到document中lyrics_div.style.width = '900px';//下面几行是设置csslyrics_div.style.backgroundColor = '#F00';lyrics_div.style.zIndex = '42';lyrics_div.style.position = 'relative';lyrics_div.style.margin = '200px auto 0';return lyrics_div;
}

根据localstorage里获取的信息，构造获取歌词的url:

DoubanFM.prototype.geci_entry_url = function(song, artist) {if (song == undefined || song == null || song == '') return '';var url = 'http://geci.me/api/lyric/' + song;if (!(artist == undefined || artist == null || artist == '')) {url += '/' + artist;}console.log(url);return url;
}

用AJAX方式异步请求歌词：

Douban.prototype.request_geci = function() {eval('var stored_song = ' + localStorage['bubbler_song_info']);//这里是重点，localstorage!console.log('the song in localStorage:' + stored_song.artist + ' ' + stored_song.song_name);if (this.tmp_song_id != stored_song.id) {console.log(this.tmp_song_id + ' is not ' + stored_song.id);var url = this.geci_entry_url(stored_song.song_name, stored_song.artist);this.tmp_song_id = stored_song.id;this.ajax_get(url);}
}

ajax请求：

DoubanFM.prototype.ajax_get = function(url) {var XHR = new XMLHttpRequest();var obj = this;//一次典型的原生js发起的AJAX请求XHR.onreadystatechange = function() {if (XHR.readyState == 4) {if (XHR.status == 200) {obj.deal_response(XHR.responseText);} else {obj.print_lyrics('获取歌词失败');}} else {obj.print_lyrics('歌词搜索中');}}XHR.open('GET', url, true);XHR.send();
}DoubanFM.prototype.deal_response = function(data) {if (this.flag == 1) {eval('var resp = ' + data);if (resp.count > 0) {this.ajax_get(resp.result[0].lrc);this.flag++;} else {this.print_lyrics('没有找到歌词');}} else {this.print_lyrics(this.format(data));this.ajax_flag = 1;}
}

对返回的歌词做处理：

DoubanFM.prototype.format = function(text) {var s = text.replace(/\[(.*)\]/g, '').trim();//去除返回数据的[]两端的内容，只保留歌词部分return s.replace(/\n/g, '\n<br />');//每行末尾输出html的换行符
}

把format过后的歌词显示在上面用document.createElement()方法创建出来的div中：

DoubanFM.prototype.print_lyrics = function(text) {this.lyrics.innerHTML = '<div id="mylrc" style="width: 490px; max-height: 280px; padding:10px; background-color: #9dd6c5; z-index: 42; po	sition: absolute; right: 0; overflow-x: hidden; overflow-y: scroll; display: block;">'+ text +'</div>';
}

最后，用setInterval()方法，每隔一秒执行就获取歌词的方法，实现豆瓣FM歌词的更新和显示：

var  fm = new DoubanFM(true);
window.setInterval(function() { fm.request_geci(); }, 1000);

至此，javascript的工作就完成了。

5.还需要什么？

写一个chrome的插件，你还需要一个manifest.json文件，类似这样：

{"name" : "Douban FM 歌词","version" : "1.0","manifest_version" : 2,"description" : "Douban FM Lrc","page_action" : {"default_icon" : "icon.png","default_title" : "Douban FM 歌词"},"permissions" : ["tabs", "http://douban.fm/", "http://*.geci.me/*"],"background" : {"scripts" : ["background.js"]},"content_scripts" : [{"matches" : ["http://douban.fm/"],"js" : ["lyrics.js"],"runat" : "document_end"}],"icons" : {"48" : "icon-48.png","128" : "icon-128.png"}
}

还需要几个不同size的icon，类似这样：