AWS Update item with list on DynamoDB using lambda Nodejs - node.js

Question

I have an item in my DynamoDB table that looks like this:
{
"qid": {
"S": "0"
},
"options": {
"L": [
{
"S": "Summer"
},
{
"S": "Winter"
}
]
},
"votes": {
"L": [
{
"N": "11"
},
{
"N": "13"
}
]
}
}
With a lambda function, I want to update one of the elements in the votes list. I want to update the index that matches the index of the option I get from the event (the event has qid, option and number of votes). So here is what I tried:
const AWS = require('aws-sdk');
const docClient = new AWS.DynamoDB.DocumentClient();
exports.handler = async (event, context) => {
const qid = event.qid;
const option = event.option;
const vote = event.vote;
const params = {
TableName : 'QnV',
Key: {
qid: qid
}
}
try {
const data = await docClient.get(params).promise()
const options = data.Item.options;
const index = options.findIndex(option)
const updateParams = {
TableName: 'QnV',
Key: {
'qid': qid
},
UpdateExpression: 'set votes[:index] = :vote',
ExpressionAttributeValues: {
':index': index,
':vote': vote
},
ReturnValues: 'UPDATED_NEW'
};
const updateData = await docClient.update(updateParams).promise();
return {
statusCode: 200,
body: JSON.stringify(updateData)
};
} catch (err) {
return {
statusCode: 500,
body: JSON.stringify(err)
};
}
};
I tried to test it with this:
{
"qid": "0",
"option": "Winter",
"vote": 14
}
But I get an error of 500 and an empty body. It looks like the update params variable is empty, but I don't understand why.
I tried to search online but it looks like I'm doing everything correctly (but if that was the case I didn't have a problem). I also didn't forget to grant permission to the function.
Edit: As suggested, I change the body of the error to err.message, and got this:
{
"statusCode": 500,
"body": "\"Winter is not a function\""
}
Please help me find the bug, I would really appreciate it!
Thank you

Answer 1

After more debugging I found the problems. There were two.
Incorrect index method.
const index = options.findIndex(option)
Changed to:
const index = options.indexOf(option)
The way I tried to find the index in updateParams was incorrect. Instead of:
UpdateExpression: 'set votes[:index] = :vote',
ExpressionAttributeValues: {
':index': index,
':vote': vote
},
It should be:
UpdateExpression: `set votes[${index}] = :vote`,
ExpressionAttributeValues: {
':vote': {N: vote},
},