Fixing JSON Data Showing undefined in JavaScript

Описание: Learn how to resolve the common issue of JSON data displaying `undefined` in JavaScript and ensure your quotes are correctly shown on your web page.
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This video is based on the question https://stackoverflow.com/q/65796690/ asked by the user 'Ashika Kamath' ( https://stackoverflow.com/u/15032110/ ) and on the answer https://stackoverflow.com/a/65796920/ provided by the user 'Kidas' ( https://stackoverflow.com/u/5427820/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing JSON Data Showing undefined in JavaScript: A Simple Guide

If you've been working with JavaScript and JSON, you may have encountered an issue where data fetched from your JSON file is showing as undefined when displayed on your webpage. This frustrating problem often arises from mismanaging the structure of your JSON and the way you retrieve this data in your JavaScript code.

In this guide, we'll explore why this happens and how to fix it so that you can successfully display your quotes on your web page.

Understanding the Problem

Let's consider the scenario: you’re attempting to display some quotes stored in a JSON file. After writing your JavaScript to fetch and manipulate this data, you find that the quotes are displaying as undefined.

What Could Be Causing This?

One of the most common reasons for this issue is that your code is trying to access a property in your JSON object that does not exist. In your case, the JSON file structure you're dealing with contains a key named quotes, but your JavaScript code mistakenly looks for a key called status.

Example of Your Initial JSON Structure

Here's your initial JSON structure, which we'll call stat.json:

[[See Video to Reveal this Text or Code Snippet]]

Issue in Your JavaScript Code

Look at this part of your JavaScript code:

[[See Video to Reveal this Text or Code Snippet]]

The problem lies in val.status—the property status does not exist in your JSON data; instead, you should be accessing val.quotes.

The Solution

To resolve this issue, you'll need to adjust your JavaScript code. Here’s how to do that:

Step 1: Modify the Mapping of JSON Data

Remove or alter the erroneous mapping line that maps JSON keys incorrectly. Simply return the data object without remapping to a new structure.

Here's how you should change it:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Ensure that You Refer to the Correct Keys in Your Code

When you map over the quotes in your paged array later in your code, make sure to access the correct property:

[[See Video to Reveal this Text or Code Snippet]]

Final JavaScript Snippet

Putting it all together, your JavaScript for retrieving and displaying quotes will look like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By correcting the JSON key in your JavaScript, you can avoid the dreaded undefined issue entirely. Be sure to validate your JSON structure and confirm you’re referencing the correct properties in your code.

With just a small adjustment, your quotes should now display correctly on your web page, allowing your users to enjoy the quotes you intended to share. Happy coding!