JavaScript+IndexedDB实现留言板:客户端存储数据

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JavaScript+IndexedDB实现留言板:客户端存储数据

来源: 作者: 时间:2016-02-21 09:50 【

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

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
  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

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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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