How to convert string to json object in javascript

Question

I have below javascript method. I try to get the id from the data parameter.

data(spark, data){
    console.log('receive ', data)
    console.log(data.id)
  }

the first output line is receive {id:1}

but the second output line is undefined

then I tried below method to convert the json string to object:

data(spark, data){
    console.log('receive ', data)
    console.log(JSON.parse(JSON.stringify(data)).id)

I still got the same output. Why can't I get the id from the input parameter?

EDIT1

I changed the parameter name to be different with the function name as below:

data(spark, d){
    console.log('receive ', d)
    console.log(JSON.parse(JSON.stringify(d)).id)
}

but I still got the same output.

Note that `id` should be wrapped in double quotes, then you can use `var json = JSON.parse(data); console.log(json.id);` — Tushar, Dec 20 '16 at 04:57
if the id is not wrapped in double quote, how to convert it to json object? — Joey Yi Zhao, Dec 20 '16 at 04:57
Why do you want to have the function name and variable name the same? — randominstanceOfLivingThing, Dec 20 '16 at 04:58
This won't work. You are using both the function name and variable name as the same string. For this kind of situation, you can do an `eval()`, but this is not at all advised. — Praveen Kumar Purushothaman, Dec 20 '16 at 04:58
Agreeing with Praveen, I'd recommend either changing the name of your argument, or changing the name of your function. It's very ambiguous as to what `data` could mean in your code, and it's better to err on the side of caution. — Jhecht, Dec 20 '16 at 05:00
I have changed the parameter name but still got the same output — Joey Yi Zhao, Dec 20 '16 at 05:02
@PraveenKumar I tried eval like this: console.log(eval(d).id) but I got the same output — Joey Yi Zhao, Dec 20 '16 at 05:05
Maybe you can consider to change the way you get this string? — Tim Tonkonogov, Dec 20 '16 at 05:08
@Sahadev the complete json string is just the first line output. It is from a websocket channel. — Joey Yi Zhao, Dec 20 '16 at 05:10

score 2 · Accepted Answer · answered Dec 20 '16 at 05:06

2

Note: Strong word of caution. Just checking if this works, and it works. Do not use it in unexpected circumstances. Very dangerous!

One crazy thing is, you forgot the function keyword, in-front of the function name.

Trying with eval() for this:

function data(spark, d) {
  // console.log('receive ', d);
  eval("d = " + d);
  console.log(d.id);
}
data("", "{id: 5}");

answered Dec 20 '16 at 05:06

Praveen Kumar Purushothaman

164,888
24
203
252

My function is defined inside a class (es6), so there is no function keyword. I tried your approach it works. but it is dangerous. Is there any other way to do that? – Joey Yi Zhao Dec 20 '16 at 05:09
With your current implementation, I am not sure if there's a valid way. – Praveen Kumar Purushothaman Dec 20 '16 at 05:10
Downvoter could tell me a reason... `:)` – Praveen Kumar Purushothaman Dec 20 '16 at 05:11
Why doesn't JSON.parse work in this case? – Joey Yi Zhao Dec 20 '16 at 05:15
@ZhaoYi It is an invalid JSON. `{id: 5}` is valid in JS, but in JSON `{"id": 5}` is valid. – Praveen Kumar Purushothaman Dec 20 '16 at 05:16
@ZhaoYi Is there anything else? – Praveen Kumar Purushothaman Dec 20 '16 at 05:18
@ZhaoYi Also check: http://stackoverflow.com/questions/41235146 – Praveen Kumar Purushothaman Dec 20 '16 at 05:20
1

The correct "solution" to this question is to have the server send down correctly formed JSON. – Dec 20 '16 at 05:44
1

@torazaburo Agreed... What if the server is not under the OP's control? – Praveen Kumar Purushothaman Dec 20 '16 at 05:45

score 0 · Answer 2 · 2016-12-20T05:52:58.893

0

Four answers:

Have the server send down properly formed JSON (with double quotes around the key names). This is the preferred solution.
Use a relaxed JSON parser. You can search and find such things on npm.
Use eval.
Do some string manipulation to enclose the id in double quotes so you can JSON.parse it, or extract the 1, or whatever you want to do. This is the least preferred solution.

edited Dec 20 '16 at 05:52

answered Dec 20 '16 at 05:47

**1.** What if the server is not under control? **2.** NPM? Seriously? – Praveen Kumar Purushothaman Dec 20 '16 at 05:49
I'm not recommending using a relaxed/dirty parser, but I think it's better than eval. What is your problem with npm? Where else would you go looking for one? – Dec 20 '16 at 05:52
I thought NPM is only for Node? Am I wrong? – Praveen Kumar Purushothaman Dec 20 '16 at 05:52
Easy enough to use node packages in the browser with something like browserify or webpack. – Dec 20 '16 at 05:53
And the crazy part is, you asked me not to use and you have added `eval()` as well. – Praveen Kumar Purushothaman Dec 20 '16 at 05:53
Not agreeing with the Webpack thing. What if it is a shared hosting? – Praveen Kumar Purushothaman Dec 20 '16 at 05:54
No, I didn't say not to use `eval`. I just said there's a better ("correct") solution. – Dec 20 '16 at 05:54
Okay... I sincerely feel that you are missing a main major point. Let's assume the worst case. OP is using a shared hosting plus the server side is not under control. What would you recommend? – Praveen Kumar Purushothaman Dec 20 '16 at 05:55
@PraveenKumar can't parse your comment about webpack. It the OP has a JS program running in a browser, then he can arrange with a bit of pre-processing to bundle a node module into his JS. This has nothing to do with where his site is hosted. – Dec 20 '16 at 05:55
I kinda feel it would be slightly dizzy for the OP. I come from JS background and started working with WebPack and other things. It feels quite annoyed to set up stuff, but since I am using a shared hosting, none of the Node stuff I can think of. Pure HTML, CSS, JS in the client side. Just my few cents of disappointment. – Praveen Kumar Purushothaman Dec 20 '16 at 05:57

mildog8 · Answer 3 · 2016-12-20T05:13:57.933

-2

eval("(" + data + ")").id is all that is required

function data(spark, data) {
  alert(eval("(" + data + ")").id);
}

data("", "{id:3}");

edited Dec 20 '16 at 05:13

answered Dec 20 '16 at 05:05

mildog8

2,030
2
22
36

I tried but got the same output – Joey Yi Zhao Dec 20 '16 at 05:05
This will work if data is `{"id":1}` but data is `{id:1}` so JSON.parse will throw an error – slebetman Dec 20 '16 at 05:05
@slebetman try it, this will work – mildog8 Dec 20 '16 at 05:11
Can the people who downvoted this answer please explain their reasons. I can't see what is wrong with it? – mildog8 Dec 20 '16 at 14:48

How to convert string to json object in javascript

3 Answers3