Getting undefined after parsing the data in node js

Question

I am trying to upload an image to S3 from a AWS lambda function. For this I have followed this tutorial - link. I have created an post API using API Gateway and written nodejs code in lambda to post an image to S3. But I am getting below error from API Gateway while trying to test the API.

"errorType": "TypeError [ERR_INVALID_ARG_TYPE]",
"errorMessage": "The first argument must be one of type string, Buffer, ArrayBuffer, Array, or Array-like Object. Received type undefined",
"code": "ERR_INVALID_ARG_TYPE",
"stack": [
    "TypeError [ERR_INVALID_ARG_TYPE]: The first argument must be one of type string, Buffer, ArrayBuffer, Array, or Array-like Object. Received type undefined",
    "    at Function.from (buffer.js:207:11)",
    "    at Runtime.exports.handler (/var/task/index.js:17:32)",
    "    at Runtime.handleOnce (/var/runtime/Runtime.js:63:25)",
    "    at process._tickCallback (internal/process/next_tick.js:68:7)"

My lambda code looks like below:-

const AWS = require('aws-sdk');
//*/ get reference to S3 client 
var s3 = new AWS.S3();


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


     let encodedImage =JSON.parse(event.body).user_avatar;
     let decodedImage = Buffer.from(encodedImage, 'base64');
     var filePath = "avatars/" + event.queryStringParameters.username + ".jpg"
     var params = {
       "Body": decodedImage,
       "Bucket": "find-my-mate-hasangi",
       "Key": filePath  
    };
    s3.upload(params, function(err, data){
       if(err) {
           callback(err, null);
       } else {
           let response = {
        "statusCode": 200,
        "headers": {
            "my_header": "my_value"
        },
        "body": JSON.stringify(data),
        "isBase64Encoded": false
    };
           callback(null, response);
    }
    });

};

I am getting error in below line:-

 let decodedImage = Buffer.from(encodedImage, 'base64');

I am passing below body from API Gateway:-

{
  "body": {
    "user_avatar": "asas"
  }
}

Update: I have tried some debugging after suggestions in comments

console.log( event.body);         // Output: { "body": { "user_avatar": "Hi There!" } }
console.log( JSON.parse(event.body)); // Output: { body: { user_avatar: 'Hi There' } } 
console.log( event.body.user_avatar);               // Output: undefined
console.log( JSON.parse(event.body).user_avatar);   // Output: undefined

The code is written in Node JS v6.10 which is not available in lambda anymore. So I am using Node JS v10.x. Can it be the reason for the error? Anyone know how to resolve the error.

Try to console.log event.body. It will help you understand the structure and the type of the body — dima golovin
– dima golovin, Commented Aug 22, 2019 at 13:17
@dimagolovin thanks for the reply. I have tried adding console.log and getting below response { "body": { "user_avatar": "Hi There!" } } — Rahul Satal
– Rahul Satal, Commented Aug 22, 2019 at 13:30
Yes user_avatar is in body. console.log(JSON.parse(event.body).user_avatar) is returning "undefined". — Rahul Satal
– Rahul Satal, Commented Aug 22, 2019 at 13:34

rkm · Accepted Answer · 2019-08-22 15:09:50Z

1

All data that you pass lives in event.body. Since you are passing object that also starts from body, you should access it like this:

JSON.parse(event.body).body.user_avatar

answered Aug 22, 2019 at 15:09

rkm

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1 Comment

Rahul Satal Over a year ago

Yes, you are right. I didn't notice it. It worked now. Thanks a lot.

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