indexed database IndexedDB

Indexed Database API 目的是提供一个可供javascript存储和检索对象，并且还能进行查询，搜索等数据库操作

设计为几乎完全异步，因此绝大部分操作都稍后执行，因此每次操作都应该提供onerror和onsuccess来处理结果

目前还没有完全支持，因此：var indexedDB = window.indexedDB || window.msIndexedDB || window.mozIndexedDB || window.webkitIndexedDB;

IndexedDB 和MySQL最大的区别在于用对象存储而不是表格来记录数据

const dbName = "the_name";

var request = indexedDB.open(dbName, 2);

request.onerror = function(event) {
// Handle errors.
};
request.onupgradeneeded = function(event) {
var db = event.target.result;

// Create an objectStore to hold information about our customers. We're
// going to use "ssn" as our key path because it's guaranteed to be
// unique.
var objectStore = db.createObjectStore("customers", { keyPath: "ssn" });

// Create an index to search customers by name. We may have duplicates
// so we can't use a unique index.
objectStore.createIndex("name", "name", { unique: false });

// Create an index to search customers by email. We want to ensure that
// no two customers have the same email, so use a unique index.
objectStore.createIndex("email", "email", { unique: true });

// Use transaction oncomplete to make sure the objectStore creation is
// finished before adding data into it.
objectStore.transaction.oncomplete = function(event) {
// Store values in the newly created objectStore.
var customerObjectStore = db.transaction("customers", "readwrite").objectStore("customers");
for (var i in customerData) {
customerObjectStore.add(customerData[i]);
}
}};