html5 初试 indexedDB(推荐)

黄舟

Lepaskan： 2017-02-20 13:24:43

asal

1480 orang telah melayarinya

indexedDB是存储大量结构化数据的API，demo中用到的是异步API，麻烦的就是所有对indexedDB的操作都会发生一个异步的‘请求’，只要熟悉了API操作起来也很简单。

大体流程是这样

1.打开数据库

var indexedDB = window.indexedDB || window.webkitIndexedDB || window.mozIndexedDB;   

      

    if (&#39;webkitIndexedDB&#39; in window) {   

        window.IDBTransaction = window.webkitIDBTransaction;   

        window.IDBKeyRange = window.webkitIDBKeyRange;   

    }   

    //这个就不解释了   

      

    var request = indexedDB.open("adsageIDB");  //open  ： indexedDB只有这一个方法  打开（数据库名）   

    request.onsuccess = function(e) { //异步   

        var v = "1.00";   

        var db = e.target.result;   

      

        if (v!= db.version) {   

            var setVrequest = db.setVersion(v);   

            setVrequest.onsuccess = function(e) { //异步   

                if(db.objectStoreNames.contains("todo")) {   

                    db.deleteObjectStore("todo");   

                }   

                var store = db.createObjectStore("todo", {keyPath: "adsid"});//onsuccess 后创建ObjectStore  暂时用到两个参数，数据库&&主键   

            }   

        }       

    }

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这样就创建/连接了一个数据库

2.创建交互对象 && 监听dom事件 && 处理数据

然后就是要操作数据库了

//插入数据 暂时只插入一列    

    var trans = db.transaction(["todo"], IDBTransaction.READ_WRITE);//创建transaction    

    var store = trans.objectStore("todo");//创建Store   

    //要操作数据必须建立transaction 和 Store   

      

    var data = {   

        "text": todoText,   

        "adsid": new Date().getTime()   

    };//一个小数据 adsid是主键   

      

    var request = store.put(data); //‘强行’插入   

      

    request.onsuccess = function(e) {   

        //成功后执行一些操作   

    };   

      

    request.onerror = function(e) {   

        console.log("Error Adding: ", e);   

    };

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//读取数据   

    var trans = db.transaction(["todo"], IDBTransaction.READ_WRITE);   

    var store = trans.objectStore("todo");   

      

    var keyRange = IDBKeyRange.lowerBound(0);   

    var cursorRequest = store.openCursor(keyRange);   

    //这里用到指针cursor ,openCursor的参数 keyRange是遍历范围 还可以添加遍历方向参数   

    //另一种方法是get() 这个就比较简单了直接store.get(&#39;键值&#39;)就行   

      

    cursorRequest.onsuccess = function(e) {   

        var result = e.target.result;   

        if(!!result == false)   

        return;   

      

        console.log(result.value);   

        result.continue(); //循环读取所有数据   

    };

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//删除数据   

    ...   

    store.delete(&#39;键值&#39;)   

    ...

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出了一个小demo

<!DOCTYPE html>  

    <html>  

      <head>  

        <script>  

          var indexedDB = window.indexedDB || window.webkitIndexedDB ||   

                          window.mozIndexedDB;   

             

          if (&#39;webkitIndexedDB&#39; in window) {   

            windowwindow.IDBTransaction = window.webkitIDBTransaction;   

            windowwindow.IDBKeyRange = window.webkitIDBKeyRange;   

          }   

             

          adsageIDB = {};   

          adsageIDB.db = null;   

             

          adsageIDB.onerror = function(e) {   

            console.log(e);   

          };   

             

          adsageIDB.open = function() {   

            var request = indexedDB.open("adsageIDB");   

             

            request.onsuccess = function(e) {   

              var v = "1.00";   

              adsageIDB.db = e.target.result;   

              var db = adsageIDB.db;   

      

              if (v!= db.version) {   

                var setVrequest = db.setVersion(v);   

             

                setVrequest.onerror = adsageIDB.onerror;   

                setVrequest.onsuccess = function(e) {   

                  if(db.objectStoreNames.contains("todo")) {   

                    db.deleteObjectStore("todo");   

                  }   

             

                  var store = db.createObjectStore("todo",   

                    {keyPath: "adsid"});   

             

                  adsageIDB.getAllTodoItems();   

                };   

              }   

              else {   

                adsageIDB.getAllTodoItems();   

              }   

            };   

             

            request.onerror = adsageIDB.onerror;   

          }   

             

          adsageIDB.addTodo = function(todoText) {   

            var db = adsageIDB.db;   

            var trans = db.transaction(["todo"], IDBTransaction.READ_WRITE);   

            var store = trans.objectStore("todo");   

             

            var data = {   

              "text": todoText,   

              "adsid": new Date().getTime()   

            };   

             

            var request = store.put(data);   

             

            request.onsuccess = function(e) {   

              adsageIDB.getAllTodoItems();   

            };   

             

            request.onerror = function(e) {   

              console.log("Error Adding: ", e);   

            };   

          };   

             

          adsageIDB.deleteTodo = function(id) {   

            var db = adsageIDB.db;   

            var trans = db.transaction(["todo"], IDBTransaction.READ_WRITE);   

            var store = trans.objectStore("todo");   

             

            var request = store.delete(id);   

             

            request.onsuccess = function(e) {   

              adsageIDB.getAllTodoItems();   

            };   

             

            request.onerror = function(e) {   

              console.log("Error Adding: ", e);   

            };   

          };   

             

          adsageIDB.getAllTodoItems = function() {   

            var todos = document.getElementById("todoItems");   

            todos.innerHTML = "";   

             

            var db = adsageIDB.db;   

            var trans = db.transaction(["todo"], IDBTransaction.READ_WRITE);   

            var store = trans.objectStore("todo");   

             

            var keyRange = IDBKeyRange.lowerBound(0);   

            var cursorRequest = store.openCursor(keyRange);   

             

            cursorRequest.onsuccess = function(e) {   

              var result = e.target.result;   

              if(!!result == false)   

                return;   

             

              renderTodo(result.value);   

              result.continue();   

            };   

             

            cursorRequest.onerror = adsageIDB.onerror;   

          };   

             

          function renderTodo(row) {   

            var todos = document.getElementById("todoItems");   

            var li = document.createElement("li");   

            var a = document.createElement("a");   

            var t = document.createTextNode(row.text);   

             

            a.addEventListener("click", function() {   

              adsageIDB.deleteTodo(row.adsid);   

            }, false);   

             

            a.textContent = " [删除]";   

            li.appendChild(t);   

            li.appendChild(a);   

            todos.appendChild(li)   

          }   

             

          function addTodo() {   

            var todo = document.getElementById("todo");   

            adsageIDB.addTodo(todo.value);   

            todo.value = "";   

          }   

             

          function init() {   

            adsageIDB.open();   

          }   

             

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

        </script>  

      </head>  

      <body>  

        <ul id="todoItems"></ul>  

        <input type="text" id="todo" name="todo" placeholder="adsageIDB text?" />  

        <input type="submit" value="增加一个 IDB" onclick="addTodo(); return false;"/>  

      </body>  

    </html>

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