Trouble parsing JSON in Node.js

Question

I am trying to parse JSON that looks like this:

{ "values" : [{ "alpha":8 },{ "beta":4 },{ "gamma":-3 } ]}

I'm parsing it with: console.log(msg.values.alpha), and get:

Missing error handler on `socket`.
TypeError: Cannot read property 'alpha' of undefined

This is how I have seen done it on other sites. Doing it with console.log(msg.values) returns undefined, and just running console.log(msg) returns proper JSON. I have seen other people with this issue, but nothing that is said to do is working. Thanks!

No, apparently that is for parsing non JSON text into JSON. @KailanBlanks Is that incorrect? If so what's the syntax? — Skyler Spaeth
– Skyler Spaeth, Commented Jan 2, 2016 at 6:00
Assuming that msg is a String with JSON, data = JSON.parse(msg) will parse it into an object. Then you will have to follow what t3dodson said in his answer. — Kailan Blanks
– Kailan Blanks, Commented Jan 2, 2016 at 6:01
So like data = JSON.parse(msg); console.log(data.values[0].alpha);? — Skyler Spaeth
– Skyler Spaeth, Commented Jan 2, 2016 at 6:04
most errors in nodejs are due to to scope , confirm that the JSON object has existence before you output it's value . try to check it's length , I guess it has not loaded or some reason like that . — Sourab Reddy
– Sourab Reddy, Commented Jan 2, 2016 at 6:07

Community · Accepted Answer · 2020-06-20 09:12:55Z

2

Don't forget to parse it to an object using JSON.parse

msg.values is an array. Technically you would have to access it via msg.values[0].alpha.

Better solution.

if you are using underscore npm install underscore

var _ = require('underscore');
var msg = JSON.parse('{ "values" : [{ "alpha":8 },{ "beta":4 },{ "gamma":-3 } ]}');
var alpha = _.find(msg.values, function (value) {
    return value.hasOwnProperty('alpha');
}).alpha;

The underscore solution would allow you to not rely on the order of the array so its probably better style.

Here is a fiddle of my code running in a browser.

edited Jun 20, 2020 at 9:12

CommunityBot

11 silver badge

answered Jan 2, 2016 at 5:58

t3dodson

4,0273 gold badges31 silver badges44 bronze badges

Sign up to request clarification or add additional context in comments.

9 Comments

t3dodson Over a year ago

@SkylerSpaeth Please see my update. The snippet I have works if you install underscore.

Skyler Spaeth Over a year ago

Ok, I will. Character limit :(

Skyler Spaeth Over a year ago

Ok, I'm still getting SyntaxError: Unexpected token C.

t3dodson Over a year ago

@SkylerSpaeth is the JSON you posted in your question the exact same as you tried? I've ran this locally and it worked. I'm making a fiddle right now.

t3dodson Over a year ago

@SkylerSpaeth I've added a link to a fiddle of the above code.

|

Collectives™ on Stack Overflow

Trouble parsing JSON in Node.js

1 Answer 1

Better solution.

9 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Better solution.

9 Comments

Your Answer

Sign up or log in

Post as a guest

Related