removeFriendByValue.js

async function removeFriendByValue(friendName: string) {
  const Key = { id: "1234" };
  // fetch the document
  let result = await DynamoDB.get({
    TableName,
    Key
  }).promise();
  // find the index
  const indexToRemove = result.Item.friends.indexOf(friendName);
  if (indexToRemove === -1) {
    // element not found
    return;
  }
  // remove-by-index
  await DynamoDB.update({
    TableName,
    Key,
    UpdateExpression: `REMOVE friends[${indexToRemove}]`,
  }).promise();
}