lambda function outputted an error "e is not a function" - amazon-web-services

Question

created two lambda functions by serverless-framework. first function "record-song-vote" writes DynamoDB, it works fine. second function "get-vote-counts" reads all records from DynamoDB, but it continually return error:
{
"errorType": "TypeError",
"errorMessage": "e is not a function",
"trace": [
"TypeError: e is not a function",
" at Runtime.handler (/var/task/serverless_sdk/index.js:9:131872)",
" at Runtime.handleOnce (/var/runtime/Runtime.js:66:25)"
]
}
function get-vote-counts:
'use strict';
const AWS = require("aws-sdk");
const dynamodb = new AWS.DynamoDB.DocumentClient();
module.exports.handler = async event => {
const params = {
TableName: process.env.DYNAMODB_TABLE
};
const result = await dynamodb.scan(params, (error, data) => {
if (error) {
console.error("Unable to update item. Error JSON:", JSON.stringify(error, null, 2));
} else {
console.log("UpdateItem succeeded:", JSON.stringify(data, null, 2));
}
}).promise();
const outputData = result["Items"].map((item) => {
return {
songName: item['songName'],
votes: item['votes']
}
});
return {
"statusCode": 200,
"headers": {
"Access-Control-Allow-Origin": "*"
},
"body": JSON.stringify(outputData)
}
};
I have tried to comment all line in this file. but I still got same error. does anybody have idea?