Issue with getting a JSON object to work in NodeJS

问题

I am trying to get a JSON object and so to make sure I had it I wrote the code like this:

var payload = JSON.parse(
JSON.stringify(Buffer.from(pubsubMessage.data, 'base64').toString())
);

console.log(payload);
// { timestamp: '1533564208', device_id: '2nd_test', temperature: '20.0' }
console.log(typeof payload);
// string

EDIT - Based on your feedback, I will elaborate further on the code and the type. Below is the full code and what it returns:

var payload = Buffer.from(pubsubMessage.data, 'base64').toString();
console.log('payload 0');
console.log(payload);
// { timestamp: "1533564208", device_id: "2nd_test", temperature: "20.0" }
console.log(typeof payload);
//string
var payload2 = JSON.parse(
  Buffer.from(pubsubMessage.data, 'base64').toString()
);
console.log('payload 2');
console.log(payload2);
// SyntaxError: Unexpected token t in JSON at position 2 at JSON.parse

EDIT 2 - To better understand the context I am using the Functions from GCloud with the PubSub trigger. So the data in the buffer is coming from pubsub.

I don't understand why the function JSON.parse crashes though it is obviously a JSON format in a string.

Any clue on this?

Thanks!

回答1:

This happened because you "stringified" twice your data, with .toString() and with JSON.stringify

// since I dont have your data, I will use this as example
var example = { a : 'a', b : 'b' };
var payload = JSON.parse(JSON.stringify(example.toString()));

// will log [object Object]
console.log(payload);
// will log string
console.log(typeof payload);

So, when you desserialize using JSON.parse, it still remains as string. You only need to serialize once:

var example = { a : 'a', b : 'b' };
var payload = JSON.parse(JSON.stringify(example));

// will log the object correctly
console.log(payload);
// will log object
console.log(typeof payload);

回答2:

The issue was sort of confusing. Hardcoded in the code the 2 below versions would give me the same result and work fine.

payload= { timestamp: "1533564208", device_id: "2nd_test", temperature: "20.0" } 

and

payload='{"timestamp":"1533564208","device_id":"2nd_test","temperature":"20.0"}'

But when using the PubSub Gcloud and the Buffer function, I had to make sure to pass in

payload='{"timestamp":"1533564208","device_id":"2nd_test","temperature":"20.0"}' 

and not

payload= { timestamp: "1533564208", device_id: "2nd_test", temperature: "20.0" } 

otherwise it would not consider it as valid JSON.

回答3:

Why do you do this ?

var payload2 = JSON.parse(
  Buffer.from(pubsubMessage.data, 'base64').toString()
);

You could just print the result of Buffer.from(pubsubMessage.data, 'base64').toString()

来源：https://stackoverflow.com/questions/51953504/issue-with-getting-a-json-object-to-work-in-nodejs