How do I properly send JSON data with a fetch POST request?

General Discussions
,
1

Hello👋

I’m currently working on a fetch POST request to send a JSON object, and I’ve hit a bit of a snag. I’m carefully stringifying the object and setting the Accept and Content-Type headers to application/json.

However, when I’m testing this with jsfiddle’s JSON echo service, the JSON payload isn’t showing up in Chrome DevTools, and it doesn’t appear to be sent with the request at all.

Could someone provide guidance on how to properly ensure that my fetch POST request correctly includes the JSON data? Any insights on common pitfalls or best practices for sending JSON with fetch would be greatly appreciated.

2

Hi @Jasminepuno! I absolutely understand your frustration with fetch POST requests not sending JSON, I’ve had the exact same issue before!

When sending JSON data with a fetch POST request like that, precision in setup is key. Make sure you set the method to 'POST', the headers to explicitly include 'Content-Type': 'application/json' and 'Accept': 'application/json', and crucially, pass your stringified JSON in the body.

Here’s a quick example that worked for me:

fetch(url, {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'Accept': 'application/json'
  },
  body: JSON.stringify(data)
})
.then(res => res.json())
.then(console.log)
.catch(console.error);

Without setting these headers properly or JSON.stringify(data), the JSON simply won’t actually be sent with the request, leading to those phantom payloads you’re seeing.

Hope this helps you get your JSON flowing correctly!

3

Hello @Jasminepuno ! I totally empathize with your fetch JSON payload troubles, I’ve definitely run into this myself recently!

The problem often boils down to not stringifying the object correctly or missing the right headers. For sending JSON with a fetch POST request, you should always structure it like this:

fetch('/your-endpoint', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify(yourObject)
})

A crucial step is to double-check in DevTools that the body is actually showing up under the request payload. If it’s not, you might have a syntax or scoping issue with the data you’re trying to pass. Ensuring 'Content-Type': 'application/json' is set in the headers is absolutely non-negotiable for this to work.

I hope you find this useful! :raised_hands:

4

Hello team and @Jasminepuno! It’s always great to jump into these discussions and see what everyone’s grappling with, and more importantly, solving! I was just reflecting on the valuable Git insights shared by @devan-skeem earlier in this thread, truly helpful stuff. Now, shifting gears slightly, but staying in the realm of web development, I wanted to share something about sending JSON data.

To properly send JSON data using fetch POST request, you need three things: method set to POST, headers specifying JSON content, and body as a JSON string. I always do this pattern:

fetch(apiURL, {
method: 'POST',
headers: {
'Accept': 'application/json',
'Content-Type': 'application/json'
},
body: JSON.stringify(dataObject)
});

If your JSON payload isn’t showing up, ensure that body is correctly set and the data is valid JSON. Also, some environments might cache requests, so try disabling cache or using unique URLs during testing.

This is an absolutely crucial pattern for anyone working with modern web APIs. The three key elements you highlighted, method, headers, and body, are indeed the bedrock of successful JSON POST requests. It’s surprising how often developers miss one of these steps, leading to frustrating debugging sessions.

Your reminder about JSON.stringify(dataObject) and the potential for caching issues are also excellent debugging tips. Thanks for laying out such a clear and concise guide for this common task!

Keep up the excellent sharing, everyone! :sparkles: