我想更新onupgradeneeded中我的indexeddb数据库的一个目标库。我想检查,如果此objecstore中存在此索引,则无法进行任何更改。但如果不是我想更新它的索引。
答案 0 :(得分:6)
var request = indexedDB.open(...);
request.onupgradeneeded = function(event) {
// Get the IDBDatabase connection
var db = event.target.result;
// This is the implied IDBTransaction instance available when
// upgrading, it is type versionchange, and is similar to
// readwrite.
var tx = event.target.transaction;
// Get the store from the transaction. This assumes of course that
// you know the store exists, otherwise use
// db.objectStoreNames.contains to check first.
var store = tx.objectStore('myStore');
// Now check if the index exists
if(store.indexNames.contains('myIndex')) {
// The store contains an index with that name
console.log('The index myIndex exists on store myStore');
// You can also access the index and ensure it has the right
// properties you want. If you want to change the properties you
// will need to delete the index then recreate it.
var index = store.index('myIndex');
// For example
if(index.multiEntry) {
console.log('myIndex is flagged as a multi-entry index');
}
if(index.unique) {
console.log('myIndex is flagged with the unique constraint');
}
} else {
// The store does not contain an index with that name
console.log('The index myIndex does not exist on store myStore');
// Can create it here if you want
store.createIndex('myIndex', ...);
}
};