Question

I have some JSON which has been passed from a servlet and is stored in xmlhttp.responseText. I want to decompose this JSON so that i can have values of data, size, style, name, etc. Also I wish to have the widget value to be in separate variable.

Here is the JSON:

{
  "widget vlaue=2": {
    "debug": "on",
    "window": {
      "title": "Sample Konfabulator Widget",
      "name": "main_window",
      "width": 500,
      "height": 500
    },
  },
  "image": { 
    "src": "Images/Sun.png",
    "name": "sun1",
    "hOffset": 250,
    "vOffset": 250,
    "alignment": "center"
  },
  "text": {
    "data": "Click Here",
    "size": 36,
    "style": "bold",
    "name": "text1",
    "hOffset": 250,
    "vOffset": 100,
    "alignment": "center",
    "onMouseUp": "sun1.opacity = (sun1.opacity / 100) * 90;"
  }
}    

I have tried this:

obj = JSON.parse(xmlhttp.responseText); 

but this failed. I could not find anything related to it online. Can anyone please help me with this?

Answer 1

From json.org :

To convert a JSON text into an object, you can use the eval()
function. eval() invokes the JavaScript compiler. Since JSON is a
proper subset of JavaScript, the compiler will correctly parse the
text and produce an object structure. The text must be wrapped in
parens to avoid tripping on an ambiguity in JavaScript’s syntax.

var myObject = eval(‘(‘ + myJSONtext + ‘)’);

However JSON.parse is still recommended:

The eval function is very fast. However, it can compile and execute
any JavaScript program, so there can be security issues. The use of
eval is indicated when the source is trusted and competent. It is much
safer to use a JSON parser. In web applications over XMLHttpRequest,
communication is permitted only to the same origin that provide that
page, so it is trusted. But it might not be competent. If the server
is not rigorous in its JSON encoding, or if it does not scrupulously
validate all of its inputs, then it could deliver invalid JSON text
that could be carrying dangerous script. The eval function would
execute the script, unleashing its malice.

To defend against this, a JSON parser should be used. A JSON parser
will recognize only JSON text, rejecting all scripts. In browsers that
provide native JSON support, JSON parsers are also much faster than
eval. It is expected that native JSON support will be included in the
next ECMAScript standard.

var myObject = JSON.parse(myJSONtext, reviver);

Perhaps there is something wrong with your JSON, visit jsonlint.com for a free web-base JSON validator.