Use JSON parse instead of eval

Question

I have this string that I generate in JAVA and pass to javascript to be parsed.

This works:

var childString = '[{title: "Item 1"},{title: "Folder 2", isFolder: true,children: [{title: "Sub-item 2.1"},{title: "Sub-item 2.2"}]},{title: "Item 3"}]'; var childArray = eval(childString);

But I've read everywhere that eval == evil so i'm looking into the JSON way of parsing. I tried using JSON.parse(childString), but I got an error.

How could I do this the JSON way?

Thanks!

@naveen: Yep, the keys have to be in double quotes. Don't understand your second comment though. — Felix Kling
– Felix Kling, Commented Aug 30, 2011 at 15:29

Matt · Accepted Answer · 2011-08-30 15:16:09Z

Your data is valid JavaScript (which is why eval works) but it is not valid JSON. For example you need to surround the name of your properties with quotes.

E.g.

'[{"title": "Item 1"} ...

You can find the JSON spec here

Icarus · Accepted Answer · 2011-08-30 15:19:40Z

You can't parse it using JSON.parse because your json string is invalid. It needs to be as follows:

var childString = '[{"title": "Item 1"},{"title": "Folder 2", "isFolder": true,"children": [{"title": "Sub-item 2.1"},{"title": "Sub-item 2.2"}]},{"title": "Item 3"}]';

See here.

FishBasketGordo · Accepted Answer · 2011-08-30 15:16:20Z

Depending on your browser, you may need to define the JSON object yourself. You can download the code for it from https://github.com/douglascrockford/JSON-js.

zzzzBov · Accepted Answer · 2011-08-30 15:16:44Z

Your JSON isn't well formed. You need double quotes on both the keys and the values.

'{"foo":"bar"}'

Femi · Accepted Answer · 2011-08-30 15:15:44Z

1

Include JSON2 in your HTML output using a script tag, and you can then use JSON.parse.

answered Aug 30, 2011 at 15:15

Femi

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Comments

Joe · Accepted Answer · 2011-08-30 15:22:55Z

Ok, jsFiddle:

var childArray = JSON.parse(childString.replace(/([{, ])([a-zA-Z0-9]+):/g, '$1"$2":'));

will work, but I might still try to get valid JSON instead.

Paul V · Accepted Answer · 2012-12-10 21:36:31Z

Note: The double quotes are imperative. THIS WOULD NOT WORK:

var childString = "[{'title': 'Item 1'},{'title': 'Folder 2', 'isFolder': true,'children': [{'title': 'Sub-item 2.1'},{'title': 'Sub-item 2.2'}]},{'title': 'Item 3'}]";

The double quotes needed to be passed within the string. So you need to single quote the object '[ ..... ]' and have the double quotes internally '[ ""...""..."" ]'.

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