CODEWITHSUNDEEP
jsonnode.jsget
Mr Boss
Mr Boss

Reputation: 769

NodeJS get request. Cannot access JSON elements

I have the following code inside a get request in NodeJS

response.on('data', function (chunk) {
    console.log(chunk);
    JSON.parse(chunk);
    console.log("ch"+chunk.product.productId);
    responseData+=chunk;
});

The first console.log prints the entire response, which is a JSON in form of a string:

{"product":[{"defaultProductUrl":"http:\/\/www.zappos.com\/product\/7306789","defaultImageUrl":"http:\/\/www.zappos.com\/images\/z\/2\/1\/3\/2\/5\/4\/2132548-p-DETAILED.jpg","productId":"7306789","productName":"Pro Short","brandId":"1630","brandName":"CW-X"}],"statusCode":"200"}

The second one however throws an error:

console.log("ch"+chunk.product.productId);

TypeError: Cannot read property 'productId' of undefined
    at IncomingMessage.<anonymous> (c:\Users\Udai\Desktop\Zappos\server.js:78:38)
    at IncomingMessage.EventEmitter.emit (events.js:95:17)
    at IncomingMessage.<anonymous> (_stream_readable.js:746:14)
    at IncomingMessage.EventEmitter.emit (events.js:92:17)
    at emitReadable_ (_stream_readable.js:408:10)
    at emitReadable (_stream_readable.js:404:5)
    at readableAddChunk (_stream_readable.js:165:9)
    at IncomingMessage.Readable.push (_stream_readable.js:127:10)
    at HTTPParser.parserOnBody [as onBody] (http.js:141:22)
    at Socket.socketOnData [as ondata] (http.js:1584:20)

Any ideas on what's going on?

Upvotes: 1

Views: 1694

Answers (2)

Jonathan Lonowski
Jonathan Lonowski

Reputation: 123513

There can be, and often are, more than a single chunk of 'data' in a readable stream. You'll want to make sure you have all of them (even if there is only 1) and perform processing once it's come to an 'end'.

var body = '';

response.on('data', function (chunk) {
    body += chunk.toString();
});

response.on('end', function () {
    // ...
});

You also need to store the result of JSON.parse() as it won't alter its argument.

var data = JSON.parse(body);

Then, from the [...] in the JSON, data.product will be an Array of Objects. So, you'll have to access an index of it to retrieve a productId.

console.log(data.product[0].productId);

Upvotes: 2

Explosion Pills
Explosion Pills

Reputation: 191779

You need to accumulate all of the data before you can run JSON.parse on it. That is, keep accumulating the chunks in responseData += chunk, then run JSON.parse. Otherwise, you could run JSON.parse on a string like: {"prop": followed by another chunk: "value"}. Neither of those are valid JSON:

response.on("end", function () {
    console.log(JSON.parse(responseData));
});

Upvotes: 2

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