JavaScript+IndexedDB实现留言板 -

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JavaScript+IndexedDB实现留言板

博客分类：

html5

html5 indexDB

indexDBInstance.html文件内容如下：

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"></meta>
<script>
	var db;
	var arrayKey=[]
	var openRequest;
	var lastCursor;
	
	var indexedDB = window.indexedDB || window.webkitIndexedDB || window.mozIndexedDB || window.msIndexedDB;
	
	function init()
	{
	    //打开数据库
	    openRequest = indexedDB.open("messageIndexDB");
	    //只能在onupgradeneeded创建对象存储空间
	    openRequest.onupgradeneeded = function(e)
	    {
	        console.log("running onupgradeneeded");
	        var thisDb = e.target.result;
	        if(!thisDb.objectStoreNames.contains("messageIndexDB"))
	        {
	            console.log("I need to create the objectstore");
	            /*
	             *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
	             *设置键名是id,并且可以自增.
	             *autoIncrement默认是false,keyPath默认null
	             */
	            var objectStore = thisDb.createObjectStore("messageIndexDB", { keyPath: "id", autoIncrement:true });
	            /*
	             *创建索引
	             *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
	             */
	            objectStore.createIndex("name", "name", { unique: false });
	        }
	    }
	
	    openRequest.onsuccess = function(e)
	    {
	        //e.target.result返回一个数据库实例
	        db = e.target.result;
	        db.onerror = function(event)
	        {
	          alert("数据库错误: " + event.target.errorCode);
	          console.dir(event.target);
	        };
	        if(db.objectStoreNames.contains("messageIndexDB"))
	        {
	            console.log("contains messageIndexDB");
	            //读写方式开启事务
	            var transaction = db.transaction(["messageIndexDB"],"readwrite");
	            transaction.oncomplete = function(event)
	            {
	                //  console.log("All done!");
	            };
	            transaction.onerror = function(event)
	            {
	                // 错误处理
	                console.dir(event);
	            };
	            //var content= document.querySelector("#content");
	
	            //得到messageIndexDB的objectStore对象
	            var objectStore = transaction.objectStore("messageIndexDB");
	
	            //游标查询
	            objectStore.openCursor().onsuccess = function(event)
	            {
	                //event.target.result获取存储空间的下一个对象
	                var cursor = event.target.result;
	                var flag=0;
	
	                //判断是否存在下一个对象,不存在是curson为null
	                if (cursor)
	                {
	                   	console.log(cursor.key); //获取键
	                    console.dir(cursor.value); //实际对象,一个Object实例
	                    var msgList= document.querySelector("#messageList");
	                    var msgDiv=document.createElement("div");
	                    var msgTxt = document.createTextNode(cursor.value[flag]["name"]+"说："+cursor.value[flag]["content"]);
	                    msgDiv.id=cursor.key;
	                    msgDiv.appendChild(msgTxt);
	                    msgList.appendChild(msgDiv);
	                    arrayKey.push(cursor.key);
	                    flag++;
	                    lastCursor=cursor.key;
	                    cursor.continue();   //将游标下移一项
	                }
	                else
	                {
	                      console.log("Done with cursor");
	                }
	            };
	            //错误处理
	             objectStore.openCursor().onerror=function(event){
	                console.dir(event);
	            };
	        }
	    };
	
	    openRequest.onerror = function (event) {
	        // 对request.error做一些需要的处理！
	        console.log("your web may not support IndexedDB,please check.");
	    };
	
	    //焦点处理
	    document.querySelector("#message").addEventListener("focus",function()
	        {
	            this.value = "";
	        });
	    document.querySelector("#name").addEventListener("focus",function()
	        {
	            this.value = "";
	        });
	
	    //添加数据
	    document.querySelector("#btn1").addEventListener("click", function()
	    {
	        var content=document.querySelector("#message").value;
	        var name=document.querySelector("#name").value;
	        /*var address=document.querySelector("#address").value;*/
	        var messageIndexDB=[{"name":name,"content":content}];
	
	        var transaction = db.transaction(["messageIndexDB"], "readwrite");
	        transaction.oncomplete = function(event)
	        {
	           // console.log("transaction complete");
	        };
	        transaction.onerror = function(event)
	        {
	            console.dir(event);
	        };
	         //得到messageIndexDB的objectStore对象
	        var objectStore = transaction.objectStore("messageIndexDB");
	        objectStore.add(messageIndexDB);
	        objectStore.openCursor().onsuccess = function(event)
	        {
	            cursor = event.target.result;
	            var key;
	            if(lastCursor==null)
	            {
	                key=cursor.key;
	                lastCursor=key;
	            }
	            else
	            {
	                key=++lastCursor;
	            }
	            var msgList= document.querySelector("#messageList");
	            var msgDiv=document.createElement("div");
	            msgDiv.id=key;
	            var msgTxt = document.createTextNode(name+"说："+content);
	            msgDiv.appendChild(msgTxt);
	            msgList.appendChild(msgDiv);
	            arrayKey.push(key);
	            console.log("success add new record!key:"+key);
	            console.dir(messageIndexDB);
	        }
	    });
	    //删除
	    document.querySelector("#delete").addEventListener("click", function()
	    {
	        if(arrayKey.length==0){
	            console.log("no data to delete!");
	        }
	        else
	        {
	            var transaction = db.transaction(["messageIndexDB"], "readwrite");
	            transaction.oncomplete = function(event)
	            {
	                   //    console.log("transaction complete!");
	            };
	
	            transaction.onerror = function(event)
	            {
	              console.dir(event);
	            };
	             //得到messageIndexDB的objectStore对象
	            var objectStore = transaction.objectStore("messageIndexDB");
	            var removeKey=arrayKey.shift();
	            //获取key
	            var getRequest=objectStore.get(removeKey);
	            getRequest.onsuccess=function(e)
	            {
	                var result =getRequest.result;
	                console.dir(result);
	            }
	            //删除key
	            var request=objectStore.delete(removeKey);
	            request.onsuccess = function(e)
	            {
	              console.log("success delete record!");
	            };
	            request.onerror = function(e)
	            {
	              console.log("Error delete record:", e);
	            };
	            //隐藏要删除的元素
	            document.getElementById(removeKey).style.display="none";
	        }
	    });
	}
	window.addEventListener("DOMContentLoaded", init, false);
</script>
<STYLE TYPE="text/css" MEDIA=screen>
	<!--
	  body{
	   font-size: 20px;
	   -webkit-text-size-adjust:none;
	  }
	-->
</STYLE>
</head>
<body>
	<h1>简单留言板（js+IndexedDB数据库实现）</h1>
	<form>
		昵称：<input id="name" type="text" name="name"><br>
		内容：<textarea id="message" rows="3" cols="20"></textarea><br>
		<input id="btn1" type="button" value="提交留言" />
		<input id="delete" type="button" value="删除留言" />
	</form>
	<br>
	<p1>留言列表</p1>
	<div id="messageList"></div>
</body>
</html>

运行效果：

点击一次“删除留言”，重新打开浏览器，数据仍然存在，如下所示：