Develop Reference

How do I fix this Unexpected token error?

Getting an error and I don't know why. Any idea?
Unexpected token / in JSON at position 233
I have found a few possible fixes and implemented them but they have not worked either.
This is the code:
const v2_ABIs = require("./Uniswap_V2_ABIs.json");
const v2abi = JSON.parse(v2_ABIs);
v2abi = v2abi.trim();
console.log(v2abi);

I had a read through the comments. If removing JSON.parse stopped causing the error. That means the JSON you where using contained something that caused a js exception when trying to parse it. If you can share the JSON I can pinpoint the exact issue, but if you don't actually need to parse it then its no problem.

JSON.parse() Error SyntaxError: Unexpected token < in JSON at position 0

I'm following along this udemy course on fullstack webdev. Fun so far until I hit this snag.
This lesson is about API and JSON and we are making a "Sign Up" email service using Mailchimp API.
I have the following constant:
And when using nodemon this is the error I get:
That app.js 43:24 points to the:
console.log(JSON.parse(data)); line.
I've checked my api key and that's correct, the options and url are set correctly.
I've been scrathing my head over this one.
Any ideas where to begin troubleshooting?

Can you do console.log(data) once and validate that data is not undefined.
If we do JSON.parse(undefined), we get the same error as the one you are getting. You can put an if block to see if data is not undefined and then selectively parse.

if(data != null){
console.log(JSON.Parse(data);
}
Check the data.

You don't need of JSON.parse(data) it because the data is already in JSON.

Uncaught SyntaxError: Unexpected token u in JSON at position 0

Only at the checkout and on individual product pages I am getting the following error in the console log:
VM35594:1 Uncaught SyntaxError: Unexpected token u in JSON at position 0
at JSON.parse (<anonymous>)
at run (layout.min.js:9)
at app.min.js:1
at main.min.js:2
at Object.execCb (require.min.js:112)
at Module.check (require.min.js:56)
at Module.<anonymous> (require.min.js:72)
at require.min.js:11
at require.min.js:74
at each (require.min.js:3)
I am using a one page checkout extension, but when I disable that the error still shows. I thought it might had something to do with the reviews on the product page (as I moved the reviews out of the tabs), but undoing that change didn't fix the error on the product pages.

Try this in the console:
JSON.parse(undefined)
Here is what you will get:
Uncaught SyntaxError: Unexpected token u in JSON at position 0
at JSON.parse (<anonymous>)
at <anonymous>:1:6
In other words, your app is attempting to parse undefined, which is not valid JSON.
There are two common causes for this. The first is that you may be referencing a non-existent property (or even a non-existent variable if not in strict mode).
window.foobar = '{"some":"data"}';
JSON.parse(window.foobarn) // oops, misspelled!
The second common cause is failure to receive the JSON in the first place, which could be caused by client side scripts that ignore errors and send a request when they shouldn't.
Make sure both your server-side and client-side scripts are running in strict mode and lint them using ESLint. This will give you pretty good confidence that there are no typos.

As #Seth Holladay #MinusFour commented, you are parsing an undefined variable.
Try adding an if condition before doing the parse.
if (typeof test1 !== 'undefined') {
test2 = JSON.parse(test1);
}
Note: This is just a check for undefined case. Any other parsing issues still need to be handled.

localStorage.clear()
That'll clear the stored data. Then refresh and things should start to work.

Your app is attempting to parse the undefined JSON web token. Such malfunction may occur due to the wrong usage of the local storage. Try to clear your local storage.
Example for Google Chrome:
F12
Application
Local Storage
Clear All

For me, that happened because I had an empty component in my page -
<script type="text/x-magento-init">
{
".page.messages": {
"Magento_Ui/js/core/app": []
}
}
Deleting this piece of code resolved the issue.

This is due to the interfering messages that come on to the page. There are multiple frames on the page which communicate with the page using window message event and object. few of them can be third party services like cookieq for managing cookies, or may be cartwire an e-com integration service.
You need to handle the onmessage event to check from where the messages are coming, and then parse the JSON accordingly.
I faced a similar problem, where one of the integration was passing a JSON object and other was passing a string starting with u

If you get Uncaught SyntaxError: Unexpected token u in JSON at position 0 then you could do the following quick checks:
jsObj = JSON.parse(data)
data - check the data is undefined or not
data - check the data is a valid JSON string or not
data - check the data is corrupted by unwanted whitespace or not
data = data.trim(); // remove the unwanted whitespace
jsObj = JSON.parse(data);
data - check the received data uses the correct encoding format('utf8', 'utf16le', 'ucs2') or not
fs.readFile(file, 'utf8', function(err, data) { ... });
fs.readFile(file, 'utf16le', function(err, data) { ... }); // le - little endian
fs.readFile(file, 'ucs2', function(err, data) { ... }); // kind of 'utf16le'

I had this issue for 2 days, let me show you how I fixed it.
This was how the code looked when I was getting the error:
request.onload = function() {
// This is where we begin accessing the Json
let data = JSON.parse(this.response);
console.log(data)
}
This is what I changed to get the result I wanted:
request.onload = function() {
// This is where we begin accessing the Json
let data = JSON.parse(this.responseText);
console.log(data)
}
So all I really did was change
this.response to this.responseText.

JSON - extract call from REST call

I am using a third party database which has a rest API. When I make a call I get an error back (which I am expecting in my case):
transaction.commit(function(err) {
if (err){
var par = JSON.parse(err); \\ returns error: SyntaxError: Unexpected token E in JSON at position 0
console.log(JSON.stringify(err));
console.log(err);
console.log('' + err);
//First console.log return: {"code":409,"metadata":{"_internal_repr":{}}}
//Second console.log return: { Error: entity already exists: app: "s~myapp"<br/>path <<br/> Element {<br/> type: "v"<br/> name: "bob#gmail.com"<br/> }<br/>><br/>
//Third console.log returns: Error: entity already exists: app: "s~myapp"<br/>path <<br/> Element {<br/> type: "v"<br/> name: "bob#gmail.com"<br/> }<br/>><br/>
}
{);
I need to extract the error field and the type field. I have tried to parse the JSON and then go par.error or par.type to get the variables, but I can't parse the object because I get an error.

You're apparently having an Error object, that has a message property to extract the message string.
Hence use
err.message
to obtain it.
References:
Error.prototype.message
Error

Based on your results, it seems that the err parameter that you're getting is already an object and not a JSON string, so you don't need to parse it at all.
You should be able to get err.code without problem.
You did mention that you need to get the error type -- but that seems to not be available in that object at all (and that's why you'd get undefined while you tried it.
However, by using err.Error you should be able to get the error string.
If you're unsure of what data the object has, you can try the following:
Execute console.dir(err) -- this should give you a good understanding of what the err object contains.
Just debug up to that point and look around in the err object.
(Best option) Check the platform's / libraries API documentation, it should tell you what error information it returns so you can use exactly that.

read/parse json data from socket in node

I have a node.js net tcp server, where I receive json data from the client(s). I would like to buffer it until the whole json block arrives, than maybe parse it, maybe just forward it to somewhere else. What modules are out there which are compatible with the latest node (0.6.x)?
Should be fast, and if it's pure js that's better for me.
b.

hum, net module for buffering, JSON.parse() for parser, sorry seems obvious but...
Check out :
https://github.com/nodejitsu/node-http-proxy
for forwarding

I have been looking at this issue for quite some hours after thinking again about it and solving it with a quite easy and straight forward solution.
My application is receiving utf-8 encoded JSON data, sometimes quite large data. In the end I also had chunks of my JSON document, which I needed to complete in order to successfully parse them.
My solution is a simple String buffer variable that I fill with the incoming data as long as I will receive an "new line" aka "\n". Then I "deliver" the data to be parsed and continue filling the buffer with next messages.
My code is as follows:
var buffer = '';
client.on('data', function(data) {
if (data.indexOf('\n') < 0) {
buffer += data;
} else {
var msg = buffer + data.substring(0, data.indexOf('\n'));
buffer = data.substring(data.indexOf('\n') + 1);
console.log('Sending msg: ' + msg);
}
}
This solution only works because my protocol is based on utf-8 and has '\n' as the delimiter.