StorageArea.get()

Retrieves one or more items from the storage area.

This is an asynchronous function that returns a Promise.

let results = browser.storage.<storageType>.get(
  keys    // null, string, object or array of strings
)

<storageType> will be one of the writable storage types — sync, local, or managed.

keys

A key (string) or keys (an array of strings, or an object specifying default values) to identify the item(s) to be retrieved from storage. If you pass an empty string, object or array here, an empty object will be retrieved. If you pass null, or an undefined value, the entire storage contents will be retrieved.

A Promise that resolves to a results object, containing every object in keys that was found in the storage area. If keys is an object, keys that are not found in the storage area will have their values given by the keys object.

If the operation failed, the promise is rejected with an error message.

If managed storage is not set, undefined will be returned.

Suppose storage contains two items:

// storage contains two items,
// "kitten" and "monster"
browser.storage.local.set({
  kitten:  {name:"Mog", eats:"mice"},
  monster: {name:"Kraken", eats:"people"}
});

Define success and failure handlers for the promise:

function onGot(item) {
  console.log(item);
}

function onError(error) {
  console.log(`Error: ${error}`);
}

With no keys argument, retrieve everything:

let gettingItem = browser.storage.local.get();
gettingItem.then(onGot, onError);

// -> Object { kitten: Object, monster: Object }

With an empty keys argument, return nothing:

// with an empty array, retrieve nothing
let gettingItem = browser.storage.local.get([]);
gettingItem.then(onGot, onError);

// -> Object { }

With the name of an object, retrieve the match:

let gettingItem = browser.storage.local.get("kitten");
gettingItem.then(onGot, onError);

// -> Object { kitten: Object }

With an array of object names, retrieve all matches:

let gettingItem = browser.storage.local.get(["kitten", "monster", "grapefruit"]);
gettingItem.then(onGot, onError);

// -> Object { kitten: Object, monster: Object } 

With an object with object names as keys and the default value as value:

let gettingItem = browser.storage.local.get({
  kitten: "no kitten",
  monster: "no monster",
  grapefruit: {
    name: "Grape Fruit",
    eats: "Water"
  }
});

// -> Object { kitten: Object, monster: Object, grapefruit: Object }

chrome.storage.local.get("kitten", function(items){
  console.log(items.kitten);  // -> {name:"Mog", eats:"mice"}
});

Or with an arrow function

chrome.storage.local.get("kitten", items => {
  console.log(items.kitten); // -> {name:"Mog", eats:"mice"}
});

Or using a Promise

let gettingItem = new Promise(resolve => chrome.storage.local.get("kitten", resolve));
gettingItem.then(onGot); // -> Object { kitten: Object }