Parse json structure with javascript

Question

Im using ajax to query a json api. It gives me a Tree like structure, which I'd like to visualize. A sample response looks like

{
  "nicos": {
    "_lastconfig_": {
      "poller": {
        "alwayspoll": [], 
        "blacklist": [], 
        "neverpoll": [
          "detector"
        ]
      }
    }, 
    "poller": {
      "alwayspoll": [], 
      "autosetup": true, 
      "blacklist": [], 
      "description": "", 
      "loglevel": "info", 
      "lowlevel": false, 
      "neverpoll": [
        "detector"
      ], 
      "poll": []
    }
  }
}

Now I'd like to parse this dynamically and visualize it as tables. A possible output could be

<h1>nicos</h1>
<h2>_last_config_</h2>
<table>
  <tr><td>alwayspoll</td><td>[]</td></tr>
  <tr><td>blacklist</td><td>[]</td></tr>
  <tr><td>neverpoll</td><td>[detector]</td></tr>
</table>
<h2>poller</h2>
<table>
  <tr><td>alwayspoll</td><td>[]</td></tr>
  <tr><td>autosetup</td><td>true</td></tr>
  <tr><td>blacklist</td><td>[]</td></tr>
  <tr><td>description</td><td></td></tr>
  <tr><td>loglevel</td><td>info</td></tr>
  <tr><td>lowlevel</td><td>false</td></tr>
  <tr><td>neverpoll</td><td>[detector]</td></tr>
  <tr><td>poll</td><td>[]</td></tr>
</table>

Since I'm a complete novice in javascript I'm asking for some advice on how I could achive that. The ajax part is not the problem, but the parsing bothers me.

Answer 1

Try this code:

function parse(obj){
    var s = '<table>';
    for(var k in obj){
        if(typeof obj[k] === 'object'){
            s += '<tr><td>'+k+'</td><td>'+parse(obj[k])+'</td></tr>\n';
        }else{
            s += '<tr><td>'+k+'</td><td>'+obj[k]+'</td></tr>\n';
        }
    }
    return s + '</table>\n';
}
parse(myJson);

Output:

    <table>
    <tr><td>nicos</td><td>
        <table>
            <tr><td>_lastconfig_</td><td>
                <table>
                    <tr><td>poller</td><td>
                        <table>
                            <tr><td>alwayspoll</td><td>
                                <table>
                                    <tr><td>0</td><td>1</td></tr>
                                    <tr><td>1</td><td>2</td></tr>
                                    <tr><td>2</td><td>3</td></tr>
                                </table>
                            </td></tr>
                            <tr><td>blacklist</td><td>
                                <table>
                                    <tr><td>0</td><td>X</td></tr>
                                    <tr><td>1</td><td>Y</td></tr>
                                    <tr><td>2</td><td>Z</td></tr>
                                </table>
                            </td></tr>
                            <tr><td>neverpoll</td><td>
                                <table>
                                    <tr><td>0</td><td>detector</td></tr>
                                </table>
                            </td></tr>
                        </table>
                    </td></tr>
                </table>
            </td></tr>
            <tr><td>poller</td><td>
                <table>
                    <tr><td>alwayspoll</td><td>
                        <table>
                        </table>
                    </td></tr>
                    <tr><td>autosetup</td><td>true</td></tr>
                    <tr><td>blacklist</td><td>
                        <table>
                        </table>
                    </td></tr>
                    <tr><td>description</td><td></td></tr>
                    <tr><td>loglevel</td><td>info</td></tr>
                    <tr><td>lowlevel</td><td>false</td></tr>
                    <tr><td>neverpoll</td><td>
                        <table>
                            <tr><td>0</td><td>detector</td></tr>
                        </table>
                    </td></tr>
                    <tr><td>poll</td><td>
                        <table>
                        </table>
                    </td></tr>
                </table>
            </td></tr>
        </table>
    </td></tr>
</table>

(I added some variables to the arrays to show that those work, too)

Answer 2

Parsing an Object to a definition list (<dl>) can be achieved with code such as this (example fiddle).

function objToDefnList(obj) { // returns a `<dl>` node (not appended to DOM Tree)
    var dl = document.createElement('dl'),
        dt, dd, key;
    for (key in obj) {
        if (obj.hasOwnProperty(key)) {
            // title
            dt = document.createElement('dt');
            dt.appendChild(document.createTextNode(key));
            dl.appendChild(dt);
            // defn.
            dd = document.createElement('dd');
            if (typeof obj[key] !== 'object') {
                dd.appendChild(document.createTextNode(obj[key].toString()));
            } else {
                dd.appendChild(objToDefnList(obj[key])); // recurse
            }
            dl.appendChild(dd);
        }
    }
    return dl; // done, return
}

It could very easily be modified to use any kind of list you want (e.g. <ul>, <ol>) or display more information (e.g. typeof obj[key]). You will probably need to style the elements, please see fiddle for an example of that, too.

Thanks to epascarello for suggesting <dl> over <ul>.

Answer 3

JSON to an HTML Table is almost surely a wheel that has been invented:

https://github.com/afshinm/Json-to-HTML-Table