IndexedDB - 使用 getAll() 函数

在前面的部分中，我们一次只从存储中检索一个对象。现在我们可以检索对象存储的所有数据或子集。get all 方法使用 getAll() 函数返回对象存储中的所有对象

句法

ObjectStore.getAll(optionalConstraint);

我们可以直接调用 getAll() 以返回对象存储中存储的所有对象，或者我们可以指定一个可选约束，例如来自汽车数据库的红色汽车

例子

在下面的示例脚本中，我们调用 getAll() 方法来一次返回对象存储中存储的所有对象 -

<!DOCTYPE html>
<html lang="en">
<head>
   <title>Document</title>
</head>
<body>
   <script>
      const request = indexedDB.open("botdatabase",1);
      request.onupgradeneeded = function(){
         const db = request.result;
         const store = db.createObjectStore("bots",{ keyPath: "id"});
         store.createIndex("branch_db",["branch"],{unique: false});
      }
      request.onsuccess = function(){
         document.write("database opened successfully");
         const db = request.result;
         const transaction=db.transaction("bots","readwrite");
         const store = transaction.objectStore("bots");
         const branchIndex = store.index("branch_db");
         store.add({id: 1, name: "jason",branch: "IT"});
         store.add({id: 2, name: "praneeth",branch: "CSE"});
         store.add({id: 3, name: "palli",branch: "EEE"});
         store.add({id: 4, name: "abdul",branch: "IT"});
         store.put({id: 4, name: "deevana",branch: "CSE"});
         const query = branchIndex.getAll(["IT"]);
         query.onsuccess = function(){
            document.write("query",query.result);
         }
         transaction.oncomplete = function(){
            db.close;
         }
      }
   </script>
</body>
</html>

输出

database opened successfully
query (1) [{...}]
arg1:(1) [{...}]
0:{id: 1, name: 'jason', branch: 'IT'}
length:1
[[Prototype]]:Array(0)
[[Prototype]]:Object