JSON.parse parsing a string into string

Question

I have confusion over the functionality of JSON.parse.

I am writing code :

dynamicMsgObj = '"rest, no disc"';
var jsonObj = {};
var isJsonString = function isJsonString(str) {
    try {
        jsonObj = JSON.parse(str);
    } catch (e) {
        return false;
    }
    return true;
}(dynamicMsgObj);
console.log(isJsonString);// returns true
console.log(typeof jsonObj);//returns string

How is this happening?? In this way I can't determine if I am receiving string or object, which is my main objective. Please help

musefan · Accepted Answer · 2015-06-23 12:47:25Z

5

That's because JSON.parse is able to successfully parse that input, it will parse it as a string and a string is what the return result will be.

Check out the documentation and look at the examples. This one specifically:

JSON.parse('"foo"'); // "foo"

And in regards to achieving your objective, you have done that already:

if(isJsonString && typeof jsonObj == 'string')
    // is string
else
    // is something else

edited Jun 23, 2015 at 12:47

answered Jun 23, 2015 at 12:42

musefan

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4 Comments

Vineet 'DEVIN' Dev Over a year ago

Is JS typecasting object into string after parsing? But why " 'foo' " doesn't work this way? How is " 'foo' " a simple string but ' "foo" ' is a json string?

musefan Over a year ago

The difference is that "foo" is valid JSON, whereas 'foo' is not. Unlike javascript, JSON does not allow " and ' to be interchangeable. What may be your confusion, and that of many, is that JSON is just a method of representing (or serializing) a javascript data object as a string. And strings are just javascript data objects like any other

Vineet 'DEVIN' Dev Over a year ago

Thanks musefan. I didn't know the JSON method's behaviour.

musefan Over a year ago

No problem, I hope you are able to implement a solution with your new understanding ;)

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