WorkletSharedStorage: get() method
==================================

**Experimental:** **This is an experimental technology**  
Check the Browser compatibility table carefully before using this in production.

 The **`get()`** method of the
 `WorkletSharedStorage` interface retrieves a value from shared storage.

Syntax
------


```js
get(key)
```

### Parameters

`key`

A string representing the key of the key-value pair you want to retrieve.

### Return value

A `Promise` that fulfills with either a string equal to the value of the retrieved key-value pair or `undefined` if the specified `key` is not found in the shared storage.

### Exceptions

`TypeError`

Thrown if:

* The worklet module has not yet been added with `addModule()`.
* `key` exceeds the browser-defined maximum length.
* The calling site does not have the Shared Storage API included in a successful privacy sandbox enrollment process.

Examples
--------

### Measuring K+ frequency

The following example measures the K+ frequency of content views. Sometimes described as "effective frequency", K frequency refers to the minimum number of views before a user will recognize or recall certain content (often used in the context of ad views).

The main page script:


```js
// k-frequency-measurement.js

async function injectContent() {
  // Load the Shared Storage worklet
  await window.sharedStorage.worklet.addModule('k-freq-measurement-worklet.js');

  // Run the K-frequency measurement operation
  await window.sharedStorage.run('k-freq-measurement', { data: { kFreq: 3, contentId: 123 });
}

injectContent();
```


The worklet module is shown below:


```js
// k-frequency-measurement-worklet.js

// Scale factor for handling noise added to data
const SCALE\_FACTOR = 65536;

/\*\*
 \* The bucket key must be a number, and in this case, it is simply the content
 \* ID itself. For more complex bucket key construction, see other use cases in
 \* this demo.
 \*/
function convertContentIdToBucket(contentId) {
  return BigInt(contentId);
}

class KFreqMeasurementOperation {
  async run(data) {
    const { kFreq, contentId } = data;

    // Read from Shared Storage
    const hasReportedContentKey = "has-reported-content";
    const impressionCountKey = "impression-count";
    const hasReportedContent =
      (await this.sharedStorage.get(hasReportedContentKey)) === "true";
    const impressionCount = parseInt(
      (await this.sharedStorage.get(impressionCountKey)) || 0,
    );

    // Do not report if a report has been sent already
    if (hasReportedContent) {
      return;
    }

    // Check impression count against frequency limit
    if (impressionCount < kFreq) {
      await this.sharedStorage.set(impressionCountKey, impressionCount + 1);
      return;
    }

    // Generate the aggregation key and the aggregatable value
    const bucket = convertContentIdToBucket(contentId);
    const value = 1 \* SCALE\_FACTOR;

    // Send an aggregatable report via the Private Aggregation API
    privateAggregation.sendHistogramReport({ bucket, value });

    // Set the report submission status flag
    await this.sharedStorage.set(hasReportedContentKey, "true");
  }
}

// Register the operation
register("k-freq-measurement", KFreqMeasurementOperation);
```


For more details about this example, see K+ frequency measurement. See the Shared Storage API landing page for links to other examples.

Specifications
--------------

| Specification |
| --- |
| Shared Storage API # dom-workletsharedstorage-get |

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

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

See also
--------

* Shared Storage API
* Noise and scaling on developer.chrome.com (2023)