lambdaPut.js

const AWS = require('aws-sdk');
const ddb = new AWS.DynamoDB.DocumentClient();

exports.handler = (event, context, callback) => {
    if (!event.requestContext.authorizer) {
        errorResponse('Authorization not configured', context.awsRequestId, callback);
        return;
    }
    const username = event.requestContext.authorizer.claims['cognito:username'];
    const requestBody = JSON.parse(event.body);
    insertItem(username, requestBody.Text).then(() => {
        callback(null, {
            statusCode: 201,
            body: JSON.stringify({}),
            headers: {
                "Access-Control-Allow-Origin": "*",
                'Access-Control-Allow-Methods': 'OPTIONS,POST,GET',
                'Access-Control-Allow-Headers': 'Origin,Content-Type,Accept'
            },
        });
    }).catch((err) => {
        console.error(err);
        errorResponse(err.message, context.awsRequestId, callback)
    });
};

function insertItem(username, text) {
    return ddb.put({
        TableName: 'Items',
        Item: {
            // Id: Math.random().toString(36).substring(2) + Date.now().toString(36),
            User: username,
            Text: text,
            Time: new Date().toISOString()
        },
    }).promise();
}

function errorResponse(errorMessage, awsRequestId, callback) {
    callback(null, {
        statusCode: 500,
        body: JSON.stringify({
            Error: errorMessage,
            Reference: awsRequestId,
        }),
        headers: {
            'Access-Control-Allow-Origin': '*',
        },
    });
}