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

7

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

answered Aug 30, 2011 at 15:16

Matt

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

3

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.

answered Aug 30, 2011 at 15:19

Icarus

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

3

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.

answered Aug 30, 2011 at 15:16

FishBasketGordo

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

3

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

'{"foo":"bar"}'

answered Aug 30, 2011 at 15:16

zzzzBov

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

1

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.

answered Aug 30, 2011 at 15:22

Joe

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

1

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'}]";

answered Dec 10, 2012 at 21:36

Paul V

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1 Comment

Paul V Over a year ago

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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