Question

I have the following JSON:

{
    "Files": {
             "Lines": {
                    "198": {
                           "firstline": "sometext"
                    }
             }
    }
}

and the value “198” is dynamic and changes. How can I access the “firstline” property easily without knowing “198” in the following code:

var schema = JSON.parse(fileContents); 
console.log(schema.Files.Lines.????.firstline);

Answer 1

A few lines will do it:

var obj = JSON.parse(your_json);
var lines = obj.Files.Lines;
var keys = Object.keys(lines);
var keyICareAbout = keys[0];
var info  = lines[keyICareAbout];

Note: This solution relies on some newer javascript features. For JSON to work in all browsers, you will need Douglas Crockford’s json2.js from here. For Object.keys to work in all browsers, use this shim from Mozilla’s JS docuentation:

if(!Object.keys) Object.keys = function(o){
 if (o !== Object(o))
      throw new TypeError('Object.keys called on non-object');
 var ret=[],p;
 for(p in o) if(Object.prototype.hasOwnProperty.call(o,p)) ret.push(p);
 return ret;
}

Edit: Try this jsfiddle. Now updated with cross browser compatability measures and accessing data dynamically.