JSON.parse — "unexpected token" with constructed JSON string

Question

This throws: "Uncaught SyntaxError: Unexpected token n(…)" ...

var text = "notation: 'fixed', precision: 2";
JSON.parse("{" + text + "}");

No clue as to why or how to safely parse.

Why not just write { notation: 'fixed', precision: 2 } as a JavaScript object literal? — Pointy
– Pointy, Commented Nov 28, 2015 at 17:07
The reason why I can't parse a JSON string to begin with is because I can't allow it in the options-string that I wish to parse. Those curly brackets are already parsed as something else, so they're are not available in the string so as to stuff JSON inside. — tobibeer
– tobibeer, Commented Nov 30, 2015 at 8:34

Moin · Accepted Answer · 2015-11-28 17:07:28Z

3

You should have tried a linter first.

The problem is that you are using single quote for key/value in your text or not using at all.

Your text should be:

var text = '"notation": "fixed", "precision": "2"';

answered Nov 28, 2015 at 17:07

Moin

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3 Comments

Andy Over a year ago

2 doesn't necessarily need to be in quotes.

Moin Over a year ago

@Andy you are right. Boolean and integers don't really need quotes.

tobibeer Over a year ago

Actually, I never knew or expected that keys in json need quotes. I see how that makes them safter (keywords), but I didn't think it was a requirement. As for which quotes, this also fails: >> var text = 'notation: "fixed", precision: 2'; JSON.parse("{" + text + "}"); <<

Oleksandr T. · Accepted Answer · 2015-11-28 17:32:33Z

1

You have wrong JSON, you should wrap keys to double quotes, like this

var text = "notation: 'fixed', precision: 2";
text = text.replace(/\'/g, '"').replace(/(\w+):/g, '"$1":');
console.log( JSON.parse("{" + text + "}") );

answered Nov 28, 2015 at 17:32

Oleksandr T.

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1 Comment

tobibeer Over a year ago

Thanks, perfect. I made it even a little more fail-proof using >> text.replace(/[\'\"]/g, '"') << so that it can be both single and double quotes.

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