IndexedDB（IndexedDB）
优质
小牛编辑
131浏览
2023-12-01
indexeddb是一种新的HTML5概念，用于将数据存储在用户的浏览器中。 indexeddb比本地存储更强大，对需要存储大量数据的应用程序很有用。 这些应用程序可以更快地运行效率和加载。
为什么要使用indexeddb？
W3C宣布Web SQL数据库是一个不推荐使用的本地存储规范，因此Web开发人员不应再使用此技术。 indexeddb是Web SQL数据库的替代方案，比旧技术更有效。
特点 (Features)
- 它存储密钥对值
- 它不是关系数据库
- IndexedDB API主要是异步的
- 它不是结构化查询语言
- 它已支持从同一域访问数据
IndexedDB (IndexedDB)
在进入indexeddb之前，我们需要添加一些实现前缀，如下所示
window.indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB ||
window.msIndexedDB;
window.IDBTransaction = window.IDBTransaction || window.webkitIDBTransaction ||
window.msIDBTransaction;
window.IDBKeyRange = window.IDBKeyRange ||
window.webkitIDBKeyRange || window.msIDBKeyRange
if (!window.indexedDB) {
window.alert("Your browser doesn't support a stable version of IndexedDB.")
}
打开IndexedDB数据库
在创建数据库之前，我们必须为数据base.let准备一些数据，从公司员工详细信息开始。
const employeeData = [
{ id: "01", name: "Gopal K Varma", age: 35, email: "contact@xnip.cn" },
{ id: "02", name: "Prasad", age: 24, email: "prasad@xnip.cn" }
];
添加数据
这里手动将一些数据添加到数据中，如下所示 -
function add() {
var request = db.transaction(["employee"], "readwrite")
.objectStore("employee")
.add({ id: "01", name: "prasad", age: 24, email: "prasad@xnip.cn" });
request.onsuccess = function(event) {
alert("Prasad has been added to your database.");
};
request.onerror = function(event) {
alert("Unable to add data\r\nPrasad is already exist in your database! ");
}
}
检索数据
我们可以使用get（）从数据库中检索数据
function read() {
var transaction = db.transaction(["employee"]);
var objectStore = transaction.objectStore("employee");
var request = objectStore.get("00-03");
request.onerror = function(event) {
alert("Unable to retrieve daa from database!");
};
request.onsuccess = function(event) {
if(request.result) {
alert("Name: " + request.result.name + ", Age:
" + request.result.age + ", Email: " + request.result.email);
} else {
alert("Kenny couldn't be found in your database!");
}
};
}
使用get（），我们可以将数据存储在对象中，而不是将数据存储在游标中，我们可以从游标中检索数据。
function readAll() {
var objectStore = db.transaction("employee").objectStore("employee");
objectStore.openCursor().onsuccess = function(event) {
var cursor = event.target.result;
if (cursor) {
alert("Name for id " + cursor.key + " is " + cursor.value.name + ",
Age: " + cursor.value.age + ", Email: " + cursor.value.email);
cursor.continue();
} else {
alert("No more entries!");
}
};
}
删除数据
我们可以使用remove（）从IndexedDB中删除数据。这是代码的样子
function remove() {
var request = db.transaction(["employee"], "readwrite")
.objectStore("employee")
.delete("02");
request.onsuccess = function(event) {
alert("prasad entry has been removed from your database.");
};
}
HTML代码
要显示我们需要使用onClick事件的所有数据，如下所示代码 -
<!DOCTYPE html>
<html>
<head>
<meta http-equiv = "Content-Type" content = "text/html; charset = utf-8" />
<title>IndexedDb Demo | onlyWebPro.com</title>
</head>
<body>
<button onclick = "read()">Read </button>
<button onclick = "readAll()"></button>
<button onclick = "add()"></button>
<button onclick = "remove()">Delete </button>
</body>
</html>
最终的代码应该是 -
<!DOCTYPE html>
<html>
<head>
<meta http-equiv = "Content-Type" content = "text/html; charset = utf-8" />
<script type = "text/javascript">
//prefixes of implementation that we want to test
window.indexedDB = window.indexedDB || window.mozIndexedDB ||
window.webkitIndexedDB || window.msIndexedDB;
//prefixes of window.IDB objects
window.IDBTransaction = window.IDBTransaction ||
window.webkitIDBTransaction || window.msIDBTransaction;
window.IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange ||
window.msIDBKeyRange
if (!window.indexedDB) {
window.alert("Your browser doesn't support a stable version of IndexedDB.")
}
const employeeData = [
{ id: "00-01", name: "gopal", age: 35, email: "gopal@xnip.cn" },
{ id: "00-02", name: "prasad", age: 32, email: "prasad@xnip.cn" }
];
var db;
var request = window.indexedDB.open("newDatabase", 1);
request.onerror = function(event) {
console.log("error: ");
};
request.onsuccess = function(event) {
db = request.result;
console.log("success: "+ db);
};
request.onupgradeneeded = function(event) {
var db = event.target.result;
var objectStore = db.createObjectStore("employee", {keyPath: "id"});
for (var i in employeeData) {
objectStore.add(employeeData[i]);
}
}
function read() {
var transaction = db.transaction(["employee"]);
var objectStore = transaction.objectStore("employee");
var request = objectStore.get("00-03");
request.onerror = function(event) {
alert("Unable to retrieve daa from database!");
};
request.onsuccess = function(event) {
// Do something with the request.result!
if(request.result) {
alert("Name: " + request.result.name + ",
Age: " + request.result.age + ", Email: " + request.result.email);
} else {
alert("Kenny couldn't be found in your database!");
}
};
}
function readAll() {
var objectStore = db.transaction("employee").objectStore("employee");
objectStore.openCursor().onsuccess = function(event) {
var cursor = event.target.result;
if (cursor) {
alert("Name for id " + cursor.key + " is " + cursor.value.name + ",
Age: " + cursor.value.age + ", Email: " + cursor.value.email);
cursor.continue();
} else {
alert("No more entries!");
}
};
}
function add() {
var request = db.transaction(["employee"], "readwrite")
.objectStore("employee")
.add({ id: "00-03", name: "Kenny", age: 19, email: "kenny@planet.org" });
request.onsuccess = function(event) {
alert("Kenny has been added to your database.");
};
request.onerror = function(event) {
alert("Unable to add data\r\nKenny is aready exist in your database! ");
}
}
function remove() {
var request = db.transaction(["employee"], "readwrite")
.objectStore("employee")
.delete("00-03");
request.onsuccess = function(event) {
alert("Kenny's entry has been removed from your database.");
};
}
</script>
</head>
<body>
<button onclick = "read()">Read </button>
<button onclick = "readAll()">Read all </button>
<button onclick = "add()">Add data </button>
<button onclick = "remove()">Delete data </button>
</body>
</html>