使用 Lambda 在 DynamoDB 的列表中查找 object 的索引

Question

I am trying to use a Lambda script to find the index of an object in a list. As an example, I would like to pass in "userid": "041c9004" and "author": "JK Rowling" and return index=1 from the books list. If the object does not exist within the books list, return index=-1 . We can assume that there will be no duplicate entries.

The structure of the DynamoDB table looks like this. Userid is the primary key.

{
  "books": [
    {
      "author": "J.R.R. Tolkien",
      "title": "Lord of the Rings"
    },
    {
      "author": "J.K Rowling",
      "title": "Harry Potter"
    },
    {
      "author": "George RR Martin",
      "title": "A Song of Ice and Fire"
    }
  ],
  "isactive": true,
  "ispublic": true,
  "lastupdated": 1597690265,
  "userid": "041c9004"
}

Here is what I have written of the Lambda function. It is returning index=-1 .

const AWS = require('aws-sdk');
const docClient = new AWS.DynamoDB.DocumentClient({region: 'us-east-1'});

exports.handler = function(event, context, callback){

    var params = {
        TableName: 'Users',
        Key: {
            userid: event.userid
        }
    };

    docClient.get(params, function(err, data){
        if(err) {
            callback(err,null);
        } else {
            callback(null, data);
            //trying to populate this variable with the correct index
            var indexOfAuthor = data.Item.books.indexOf(event.author); 
            console.log('The index of the author is ' + indexOfAuthor);
        }
    });
};

Answer 1

Assuming event.author is just the author name, you could try:

data.Item.books.findIndex(i => i.author === event.author)