function main(projectId, operationString) {
  // [START compute_instances_operation_check]
  /**
   * TODO(developer): Uncomment and replace these variables before running the sample.
   */
  // const projectId = 'YOUR_PROJECT_ID';
  // const operationString = 'YOUR_OPERATION_STRING'

  const compute = require('@google-cloud/compute');

  // Parse stringified operation to the object instance.
  let operation = JSON.parse(operationString);

  async function waitForOperation() {
    const operationsClient = new compute.ZoneOperationsClient();

    while (operation.status !== 'DONE') {
      [operation] = await operationsClient.wait({
        operation: operation.name,
        project: projectId,
        zone: operation.zone.split('/').pop(),
      });
    }

    console.log('Operation finished.');
  }

  waitForOperation();
  // [END compute_instances_operation_check]
}
Waits for an operation to be completed. Calling this function will block until the operation is finished.
@param {string} projectId - ID or number of the project you want to use.
@param {string} operationString - Operation instance you want to wait in string format.