WorkletSharedStorage: get() method

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

Syntax

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:

// 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:

// 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,
      10,
    );

    // 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

Browser compatibility

See also

• Shared Storage API
• Noise and scaling on privacysandbox.google.com (2023)