IDBRequest: error event
=======================

The `error` handler is executed when an error caused a request to fail.

This event is not cancelable and does not bubble.

Syntax
------

Use the event name in methods like `addEventListener()`, or set an event handler property.


```js
addEventListener("error", (event) => {});

onerror = (event) => {};
```

Event type
----------

A generic `Event`.

Examples
--------

This example opens a database and tries to add a record, listening for the `error` event for the `add()` operation (this will occur if, for example, a record with the given `taskTitle` already exists):


```js
// Open the database
const DBOpenRequest = window.indexedDB.open("toDoList", 4);

DBOpenRequest.addEventListener("upgradeneeded", (event) => {
  const db = event.target.result;

  db.onerror = () => {
    console.log("Error creating database");
  };

  // Create an objectStore for this database
  const objectStore = db.createObjectStore("toDoList", {
    keyPath: "taskTitle",
  });

  // define what data items the objectStore will contain
  objectStore.createIndex("hours", "hours", { unique: false });
  objectStore.createIndex("minutes", "minutes", { unique: false });
  objectStore.createIndex("day", "day", { unique: false });
  objectStore.createIndex("month", "month", { unique: false });
  objectStore.createIndex("year", "year", { unique: false });
});

DBOpenRequest.addEventListener("success", (event) => {
  const db = DBOpenRequest.result;

  // open a read/write db transaction, ready for adding the data
  const transaction = db.transaction(["toDoList"], "readwrite");
  const objectStore = transaction.objectStore("toDoList");
  const newItem = {
    taskTitle: "my task",
    hours: 10,
    minutes: 10,
    day: 10,
    month: "January",
    year: 2020,
  };

  const objectStoreRequest = objectStore.add(newItem);
  objectStoreRequest.addEventListener("error", () => {
    console.log(`Error adding new item: ${newItem.taskTitle}`);
  });
});
```


The same example, using the `onerror` property instead of `addEventListener()`:


```js
// Open the database
const DBOpenRequest = window.indexedDB.open("toDoList", 4);

DBOpenRequest.onupgradeneeded = (event) => {
  const db = event.target.result;

  db.onerror = () => {
    console.log("Error creating database");
  };

  // Create an objectStore for this database
  const objectStore = db.createObjectStore("toDoList", {
    keyPath: "taskTitle",
  });

  // define what data items the objectStore will contain
  objectStore.createIndex("hours", "hours", { unique: false });
  objectStore.createIndex("minutes", "minutes", { unique: false });
  objectStore.createIndex("day", "day", { unique: false });
  objectStore.createIndex("month", "month", { unique: false });
  objectStore.createIndex("year", "year", { unique: false });
};

DBOpenRequest.onsuccess = (event) => {
  const db = DBOpenRequest.result;

  // open a read/write db transaction, ready for adding the data
  const transaction = db.transaction(["toDoList"], "readwrite");
  const objectStore = transaction.objectStore("toDoList");
  const newItem = {
    taskTitle: "my task",
    hours: 10,
    minutes: 10,
    day: 10,
    month: "January",
    year: 2020,
  };

  const objectStoreRequest = objectStore.add(newItem);
  objectStoreRequest.onerror = () => {
    console.log(`Error adding new item: ${newItem.taskTitle}`);
  };
};
```

Browser compatibility
---------------------

BCD tables only load in the browser with JavaScript enabled. Enable JavaScript to view data.

See also
--------

* Using IndexedDB