Unexpected end of JSON input - Hyperledger Fabric while using putState()

Question

async changeCarOwner(ctx, carNumber, newOwner) {

        const carAsBytes = await ctx.stub.getState(carNumber); 
        if (!carAsBytes || carAsBytes.length === 0) {
            throw new Error(`${carNumber} does not exist`);
        }
        const car = JSON.parse(carAsBytes.toString());
        car.owner = newOwner

        await ctx.stub.putState(carNumber, Buffer.from(JSON.stringify(car)));

    }

}

I keep getting an error: Unexpected end of JSON input. Why? I am trying to update an existing key-value pair in couchDb using the above code.

Answer 1

This error happens at this line:

const car = JSON.parse(carAsBytes.toString());

It is due to the fact that carAsBytes.toString() does not evaluates to a properly formatted JSON string. The code you show seems fine, but the error is coming from elsewhere in your code.

Debugging tip: use the debugger statement to examine variables before the faulty line, simply add a console.log(carAsBytes.toString()) before it.