ReactJS and Node.JS: Troubleshooting “JSON.parse: unexpected character at line 1 column 1 of the JSON data” Error

Are you encountering the dreaded “JSON.parse: unexpected character at line 1 column 1 of the JSON data” error while working with ReactJS and Node.JS? Don’t worry, you’re not alone. This error can be quite frustrating, but with a closer look and some troubleshooting, we can find a solution together.

Understanding the Error

The “JSON.parse: unexpected character at line 1 column 1 of the JSON data” error typically occurs when there is an issue with parsing the JSON data received from the server. It indicates that the JSON data being passed to JSON.parse() is invalid, resulting in a parsing error.

Analyzing the Code

Let’s take a look at two different code implementations and try to identify the cause of the error.

Implementation 1: Login Function

In this implementation, the login function works correctly, and the JSON data is parsed without any issues. The code snippet for the Node.js route and ReactJS login function is as follows:

code


















































































// Node.js Route for login
const router = require('express').Router();
const User = require('user');

router.post("/login", async (req, res) => {
    try {
        await User.findOne({
            where: {
                email: req.body.email,
                password: req.body.password,
            }
        }).then((user) => {
            if (!user) {
                return res.send({message: "Login error!"});
            } else {
                const userData = {id: user.id, email: user.email};
                res.send({"user": userData});
            }
        }).catch((err) => {
            return res.send(err);
        });
    } catch (err) {
        return res.send(err);
    }
});

// ReactJS for login
loginFunction(e, data) {
    e.preventDefault();
    fetch('http://localhost:4500/login', {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json'
        },
        body: JSON.stringify(data)
    })
        .then(response => response.json())
        .then(json => {
            this.setState({'user': json['user'] 





});
        })
        .catch((err) => {
            console.log(err);
            this.setState({errors: "Login error"})
        });
}

Implementation 2: Posts Function

In this implementation, the error occurs when trying to retrieve posts. The code snippet for the Node.js route and ReactJS posts function is as follows:

code

































// Node.JS for Posts
const router = require('express').Router();
const Post = require('post');

router.get("/posts", async (req, res) => {
    try {
        await Post.findAndCountAll()
            .then((posts) => {
                res.send({"posts": posts});
            }).catch((err) => {
                return res.send(err);
            });
    } catch (err) {
        return res.send(err);
    }
});

// ReactJS for Posts
postsFunction() {
    fetch('http://localhost:4500/posts', {
        method: 'GET',
        headers: {
            'Content-Type': 'application/json'
        }
    })
        .then(response => response.json())
        .then(json => {
            this.setState({'posts': json.posts.rows});
        })
        .catch((err) => {
            console.log(err);
            this.setState({errors: "Posts error."})
        });
}

Analyzing the Differences

Upon analyzing the code, we can identify the differences between the two implementations that might be causing the error:

1. HTTP Method: The login function uses the POST method, while the posts function uses the GET method.
2. Response Parsing: Both functions utilize the response.json() method to parse the JSON data returned by the server.
3. Route URL: The login function uses the correct route URL (/login), while the posts function seems to have an issue with the URL (/undefined/posts).

Finding the Solution

Now that we have identified the differences, let’s focus on resolving the issue with the posts function.

Issue: Incorrect Route URL

The error message mentions an unexpected concatenation of the React URL, undefined, and the Node.JS route path. This indicates that the process.env.API_URL is not defined properly, resulting in an undefined URL.

Solution: Check Environment Variable

To resolve this issue, ensure that the environment variable REACT_APP_API_URL is set correctly. In ReactJS projects, environment variables should start with the prefix REACT_APP_ for them to be recognized.

Update the posts function in your ReactJS code as follows:

code
















// ReactJS for Posts
postsFunction() {
    fetch(process.env.REACT_APP_API_URL + '/posts', {
        method: 'GET',
        headers: {
            'Content-Type': 'application/json'
        }
    })
        .then(response => response.json())
        .then(json => {
            this.setState({'posts': json.posts.rows});
        })
        .catch((err) => {
            console.log(err);
            this.setState({errors: "Posts error."})
        });
}

Ensure that you have the correct value set for REACT_APP_API_URL in your environment configuration.

Conclusion

By identifying the differences and addressing the issue with the route URL, you can troubleshoot and resolve the “JSON.parse: unexpected character at line 1 column 1 of the JSON data” error. Remember to review your code carefully, check environment variables, and ensure proper JSON parsing to avoid such errors.

Now you can continue developing your ReactJS and Node.JS application without being hindered by this parsing error.