Question

I’m attempting to convert a JSON object to a “normal” object using the following…

        var slaobj = eval('('+s+')');

s being the JSON. however, it doesnt seem to work (It’s `.length’ is coming back as undefined). What am I doing wrong?

Answer 1

It’s `.length’ is coming back as undefined

It won’t necessarily have a length property, unless it’s an array or some other object that has one. For example:

var json = '{"foo": "Value of foo"}';
var obj = eval('(' + json + ')');
alert(obj.foo); // alerts "value of foo"
alert(obj.length); // alerts "undefined", there's no `length` in `obj`

Live example

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Off-topic: Using eval to deserialize JSON text can be a security problem, unless you can unambiguously trust the source of the JSON text (for instance, it’s your own server and you’re connecting via SSL), because eval doesn’t parse JSON, it parses and runs JavaScript code. (Adding the parentheses doesn’t really help.) You can get alternatives to using eval from Douglas Crockford’s Github page (he’s the inventor of JSON). Last I checked, there are three alternatives there, two of which don’t use eval at all; see the README at the bottom of the page for details.