removeWithVersionCondition.js

async function conditionalVersionRemoveFriendByValue(friendName) {
  const Key = { id: "1234" };
  
  // fetch the document
  const document = (await DynamoDB.get({
    TableName,
    Key
  }).promise()).Item;
  
  // find the index
  let indexToRemove = document.friends.indexOf(friendName);
  let version = document.version;
  if (indexToRemove === -1) {
    // element not found
    return false;
  }
  
  // remove-by-index IFF the version field matches
  const { err, data } = await updateWithErrorWrapper({
    TableName,
    Key,
    UpdateExpression: `
      REMOVE friends[${indexToRemove}]
      ADD version :incrementVersionBy
    `,
    ConditionExpression: `version = :version`,
    ExpressionAttributeValues: {
      ":version": version,
      ":incrementVersionBy": 1
    }
  });
  
  if (err) {
    if (err.code === "ConditionalCheckFailedException") {
      console.error("condition expression failed");
    } else {
      console.error("unhandled error: " + err);
    }
    return false;
  }
  return true;
}