How to extract specific fields from API response using Node.js

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1

I’m working with a financial data API in Node.js and getting JSON responses back, but I’m having trouble accessing individual properties from the result.

When I try to access array elements by index, I get single characters instead of the objects I expect. Here’s my current setup:

const express = require('express');
const https = require('https');
const app = express();

app.post('/financial-data', function(req, res){
    const requestOptions = {
        "method": "GET",
        "hostname": "api.example.com",
        "path": "/v1/financial/MSFT",
        "headers": {
            "Authorization": "Bearer your-token-here",
            "Content-Type": "application/json"
        }
    };

    const apiRequest = https.request(requestOptions, function (apiResponse) {
        const dataChunks = [];
        
        apiResponse.on("data", function (dataChunk) {
            console.log(dataChunk.toString()[15]); // This prints a single letter
            dataChunks.push(dataChunk);
        });

        apiResponse.on("end", function () {
            const completeData = Buffer.concat(dataChunks);
            // How do I properly parse this to access specific fields?
        });
    });
    
    apiRequest.end();
});

The API returns data structured like this:

[{
  "companySymbol": "MSFT",
  "reportDate": "2023-06-30",
  "totalRevenue": 211915000000,
  "totalAssets": 411976000000,
  "totalDebt": 47032000000,
  "cashBalance": 29263000000
}, ...]

I want to extract specific values like totalDebt from the first object, but when I try dataChunk[0], I just get individual characters. What’s the correct way to parse and access these nested properties?

2

Ah, I see what’s wrong! You’re treating the raw buffer like it’s already parsed JSON. After concatenating all the chunks, you need to run JSON.parse(completeData.toString()) first. Then you can access properties normally like parsedData[0].totalDebt. You’re getting individual characters because you’re indexing into the string before parsing it.

3

You’re mixing up string indexing with array indexing. When you do dataChunk.toString()[15], you’re grabbing the 15th character of the JSON string - not the 15th array element. I’ve done this same thing working with REST APIs.

Here’s the fix: concatenate your chunks first, convert to string, then parse as JSON. After that you can access your data properties.

const result = JSON.parse(completeData.toString());
const debt = result[0].totalDebt;

Also throw some error handling around JSON.parse - malformed responses will crash your app.

4

You’re trying to access array indices on raw string data. Parse the full response first. Here’s what to do in your end event handler:

apiResponse.on("end", function () {
    const completeData = Buffer.concat(dataChunks);
    const jsonData = JSON.parse(completeData.toString());
    const firstCompany = jsonData[0];
    const totalDebt = firstCompany.totalDebt;
    console.log(totalDebt); // Now you'll get the actual number
});

I hit this same issue with crypto APIs last year. HTTP responses come in chunks as raw bytes, so you’ve got to reassemble everything before parsing. When you check dataChunk.toString()[15], you’re looking at individual characters in incomplete JSON - that’s why you’re seeing letters instead of objects.

5

Everyone covered parsing well, but here’s my approach for financial API integrations.

You’ll hit this pattern constantly - fetch data, parse responses, transform fields, maybe store results. Custom Node.js handlers for each endpoint? Gets messy quick.

I automate the whole thing instead. Set up a scenario that handles HTTP requests, auto-parses JSON responses, grabs whatever fields you need (like totalDebt), and stores or forwards data to other systems.

No more chunks, buffers, or parsing headaches. Configure your data flow visually and let it run. Way cleaner than maintaining Express routes for every financial endpoint.

Scales better too. Need historical data, real-time updates, or multiple financial APIs? Just extend the automation instead of rewriting code.

6

You’re indexing the raw string before converting it. Get all your chunks concatenated first, then do const parsed = JSON.parse(completeData.toString()). After that, parsed[0].totalDebt works fine. Same thing happened to me with payment APIs - parse first!