带有节点JS抛出错误的Dynamo DB getItem

Question

I am new to Javascript and DynamoDB. I am trying to perform getitem using aws-sdk for javascript in nodejs. primary index of Dynamo table Cars is "name" a string.

var AWS = require('aws-sdk');
AWS.config.region='eu-west-1';
var db = new AWS.DynamoDB();

var params = {
TableName : 'Cars',
            Key : {
                    "name" : {
                            "S" : "Volkswagen Dasher"
                    },
            }
}

db.getItem(params, function(err, data) {
                if (err) {
                console.log(err); // an error occurred
                }
                else {
                console.log(data); // successful response
                }
                return next();
                });

On running the above .js file I am getting the following error.

 ubuntu@ubuntu:~/node$ node getItem.js  
 {}
 /home/ubuntu/node_modules/aws-sdk/lib/request.js:30
             throw err;
                   ^ ReferenceError: next is not defined
     at Response.<anonymous> (/home/ubuntu/node/getItem.js:21:10)
     at Request.<anonymous> (/home/ubuntu/node_modules/aws-sdk/lib/request.js:353:18)
     at Request.callListeners (/home/ubuntu/node_modules/aws-sdk/lib/sequential_executor.js:105:20)
     at Request.emit (/home/ubuntu/node_modules/aws-sdk/lib/sequential_executor.js:77:10)
     at Request.emit (/home/ubuntu/node_modules/aws-sdk/lib/request.js:595:14)
     at Request.transition (/home/ubuntu/node_modules/aws-sdk/lib/request.js:21:10)
     at AcceptorStateMachine.runTo (/home/ubuntu/node_modules/aws-sdk/lib/state_machine.js:14:12)
     at /home/ubuntu/node_modules/aws-sdk/lib/state_machine.js:26:10
     at Request.<anonymous> (/home/ubuntu/node_modules/aws-sdk/lib/request.js:37:9)
     at Request.<anonymous> (/home/ubuntu/node_modules/aws-sdk/lib/request.js:597:12)

Plz help me out. Cheers!

Answer 1

Glad to see you're giving DynamoDB a try! I'm not really sure I understand the context of your code, but if your goal is to make a simple GetItem call, you don't need the 'return next()' statement. Given javascript's event driven nature, these callbacks are asynchronous and don't really "return" anything. Instead, you should inspect the response (data) and perform an action accordingly.

IE

dynamoDB.getItem(params, function(err, data) {
                     if (data) {
                        doSomethingWithItem(data.Item);
                     }
                 });

Also, if you're just starting out I would recommend taking a look at the document-js-sdk which a wrapper on top of the original SDK to allow you to use literals such as "string" instead of {S: "string"}.