JavaScript+IndexedDB实现留言板：客户端存储数据

之前看到贴友有问：用js怎么实现留言板效果。当时也写了一个，但是没有实现数据存储：http://www.ido321.com/591.html

现在将之前的改写一下，原来的HTML布局不变，为了防止Google调整字体,在原来的css中加入一个样式

   1: body{

   2:     font-size: 20px;

   3:     -webkit-text-size-adjust:none;

   4: }

在google中调整字体，可以见此文：http://www.ido321.com/652.html     有评论说不行，但是LZ在这个实例中测试了，是可以的

重点是js，完整的js代码修改如下：

   1:

   2:     var db;

   3:     var arrayKey=[]

   4:     var openRequest;

   5:     var lastCursor;

   6:

   7:     var indexedDB = window.indexedDB || window.webkitIndexedDB || window.mozIndexedDB || window.msIndexedDB;

   8:

   9:     function init()

  10:     {

  11:         //打开数据库

  12:         openRequest = indexedDB.open("messageIndexDB");

  13:         //只能在onupgradeneeded创建对象存储空间

  14:         openRequest.onupgradeneeded = function(e)

  15:         {

  16:             console.log("running onupgradeneeded");

  17:             var thisDb = e.target.result;

  18:             if(!thisDb.objectStoreNames.contains("messageIndexDB"))

  19:             {

  20:                 console.log("I need to create the objectstore");

  21:                 /*

  22:                  *创建对象存储空间，第一个参数必须和打开数据库的第一个参数一致

  23:                  *设置键名是id,并且可以自增.

  24:                  *autoIncrement默认是false,keyPath默认null

  25:                  */

  26:                 var objectStore = thisDb.createObjectStore("messageIndexDB", { keyPath: "id", autoIncrement:true });

  27:                 /*

  28:                  *创建索引

  29:                  *第一个参数是索引名,第二个是属性名,第三个设置索引特性

  30:                  */

  31:                 objectStore.createIndex("name", "name", { unique: false });

  32:             }

  33:         }

  34:

  35:         openRequest.onsuccess = function(e)

  36:         {

  37:             //e.target.result返回一个数据库实例

  38:             db = e.target.result;

  39:             db.onerror = function(event)

  40:             {

  41:               alert("数据库错误: " + event.target.errorCode);

  42:               console.dir(event.target);

  43:             };

  44:             if(db.objectStoreNames.contains("messageIndexDB"))

  45:             {

  46:                 console.log("contains messageIndexDB");

  47:                 //读写方式开启事务

  48:                 var transaction = db.transaction(["messageIndexDB"],"readwrite");

  49:                 transaction.oncomplete = function(event)

  50:                 {

  51:                     //  console.log("All done!");

  52:                 };

  53:                 transaction.onerror = function(event)

  54:                 {

  55:                     // 错误处理

  56:                     console.dir(event);

  57:                 };

  58:                 var content= document.querySelector("#content");

  59:

  60:                 //得到messageIndexDB的objectStore对象

  61:                 var objectStore = transaction.objectStore("messageIndexDB");

  62:

  63:                 //游标查询

  64:                 objectStore.openCursor().onsuccess = function(event)

  65:                 {

  66:                     //event.target.result获取存储空间的下一个对象

  67:                     var cursor = event.target.result;

  68:                     var flag=0;

  69:

  70:                     //判断是否存在下一个对象,不存在是curson为null

  71:                     if (cursor)

  72:                     {

  73:                           console.log(cursor.key); //获取键

  74:                           console.dir(cursor.value); //实际对象,一个Object实例

  75:                         var msgList= document.querySelector("#messageList");

  76:                         var msgDiv=document.createElement("div");

  77:                         var msgTxt = document.createTextNode(cursor.value[flag]["name"]+"说："+cursor.value[flag]["content"]);

  78:                         msgDiv.id=cursor.key;

  79:                         msgDiv.appendChild(msgTxt);

  80:                         msgList.appendChild(msgDiv);

  81:                         arrayKey.push(cursor.key);

  82:                         flag++;

  83:                         lastCursor=cursor.key;

  84:                         cursor.continue();   //将游标下移一项

  85:                     }

  86:                     else

  87:                     {

  88:                           console.log("Done with cursor");

  89:                     }

  90:                 };

  91:                 //错误处理

  92:                  objectStore.openCursor().onerror=function(event){

  93:                     console.dir(event);

  94:                 };

  95:             }

  96:         };

  97:

  98:         openRequest.onerror = function (event) {

  99:             // 对request.error做一些需要的处理！

 100:             console.log("your web may not support IndexedDB,please check.");

 101:         };

 102:

 103:         //焦点处理

 104:         document.querySelector("#message").addEventListener("focus",function()

 105:             {

 106:                 this.value = "";

 107:             });

 108:         document.querySelector("#name").addEventListener("focus",function()

 109:             {

 110:                 this.value = "";

 111:             });

 112:

 113:         //添加数据

 114:         document.querySelector("#btn1").addEventListener("click", function()

 115:         {

 116:             var content=document.querySelector("#message").value;

 117:             var name=document.querySelector("#name").value;

 118:             /*var address=document.querySelector("#address").value;*/

 119:             var messageIndexDB=[{"name":name,"content":content}];

 120:

 121:             var transaction = db.transaction(["messageIndexDB"], "readwrite");

 122:             transaction.oncomplete = function(event)

 123:             {

 124:                // console.log("transaction complete");

 125:             };

 126:             transaction.onerror = function(event)

 127:             {

 128:                 console.dir(event);

 129:             };

 130:              //得到messageIndexDB的objectStore对象

 131:             var objectStore = transaction.objectStore("messageIndexDB");

 132:             objectStore.add(messageIndexDB);

 133:             objectStore.openCursor().onsuccess = function(event)

 134:             {

 135:                 cursor = event.target.result;

 136:                 var key;

 137:                 if(lastCursor==null)

 138:                 {

 139:                     key=cursor.key;

 140:                     lastCursor=key;

 141:                 }

 142:                 else

 143:                 {

 144:                     key=++lastCursor;

 145:                 }

 146:                 var msgList= document.querySelector("#messageList");

 147:                 var msgDiv=document.createElement("div");

 148:                 msgDiv.id=key;

 149:                 var msgTxt = document.createTextNode(name+"说："+content);

 150:                 msgDiv.appendChild(msgTxt);

 151:                 msgList.appendChild(msgDiv);

 152:                 arrayKey.push(key);

 153:                 console.log("success add new record!key:"+key);

 154:                 console.dir(messageIndexDB);

 155:             }

 156:         });

 157:         //删除

 158:         document.querySelector("#delete").addEventListener("click", function()

 159:         {

 160:             if(arrayKey.length==0){

 161:                 console.log("no data to delete!");

 162:             }

 163:             else

 164:             {

 165:                 var transaction = db.transaction(["messageIndexDB"], "readwrite");

 166:                 transaction.oncomplete = function(event)

 167:                 {

 168:                        //    console.log("transaction complete!");

 169:                 };

 170:

 171:                 transaction.onerror = function(event)

 172:                 {

 173:                   console.dir(event);

 174:                 };

 175:                  //得到messageIndexDB的objectStore对象

 176:                 var objectStore = transaction.objectStore("messageIndexDB");

 177:                 var removeKey=arrayKey.shift();

 178:                 //获取key

 179:                 var getRequest=objectStore.get(removeKey);

 180:                 getRequest.onsuccess=function(e)

 181:                 {

 182:                     var result =getRequest.result;

 183:                     console.dir(result);

 184:                 }

 185:                 //删除key

 186:                 var request=objectStore.delete(removeKey);

 187:                 request.onsuccess = function(e)

 188:                 {

 189:                   console.log("success delete record!");

 190:                 };

 191:                 request.onerror = function(e)

 192:                 {

 193:                   console.log("Error delete record:", e);

 194:                 };

 195:                 //隐藏要删除的元素

 196:                 document.getElementById(removeKey).style.display="none";

 197:             }

 198:         });

 199:     }

 200:     window.addEventListener("DOMContentLoaded", init, false);

要注意一点的是，在创建对象存储空间的时候，必须在openRequest.onupgradeneeded 中创建，否则出错

FF4+，和google支持IndexedDB，IE10+据说支持，但LZ测试了，不支持，有错误还请指正。

由于IndexedDB不能实现共享，所以每个客户端打开时IndexedDB保存的数据不一致,LZ是在Google中测试的，打开控制台，查看数据如下

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来源：http://www.ido321.com/660.html