Flattens multi-level JSON objects (useful for converting complex JSON to CSV format)

flattenjson.html

<style>
textarea { height: 400px; width: 100%; }
</style>
<h1>flatten json</h1>
<textarea id="data">[]</textarea>
<button id="goByLine">line-by-line</button>
<button id="goWhole">as whole object</button>

<textarea id="result"></textarea>

<small>
  Flattens multi-level JSON objects (useful for converting complex JSON to CSV format).
  With line-by-line, make sure you don't have a blank last line or you'll get <em>unexpected end of input</em>.
  Further problems, as always, check the console.
</small>

<script>
document.getElementById('goByLine').addEventListener('click', function () {
  var dataList = document.getElementById('data').value,
      result = '';

  try {
    dataList = dataList.split(/[\r\n]+/);
    for (var i in dataList)
    {
      if (dataList[i].length !== undefined && dataList[i].length == 0)
        continue;

      var thisObj = JSON.parse(dataList[i]);
      console.log('parsing line', i, thisObj);
      result = result + JSON.stringify(flatten(thisObj)) +"\n";
    }

    console.log('we did it', i);
    document.getElementById('result').value = result;
  }
  catch (e) {
    document.getElementById('result').value = "Error: "+ e;
  }
});

document.getElementById('goWhole').addEventListener('click', function () {
  var data = document.getElementById('data').value,
      result = '';

  try {
    var thisObj = JSON.parse(data);
    console.log('parsing object', thisObj);
    result = result + JSON.stringify(flatten(thisObj));

    console.log('we did it');
    document.getElementById('result').value = result;
  }
  catch (e) {
    document.getElementById('result').value = "Error: "+ e;
  }
});

// http://stackoverflow.com/questions/19098797/fastest-way-to-flatten-un-flatten-nested-json-objects
var flatten = (function (isArray, wrapped) {
    return function (table) {
        return reduce("", {}, table);
    };

    function reduce(path, accumulator, table) {
        if (isArray(table)) {
            var length = table.length;

            if (length) {
                var index = 0;

                while (index < length) {
                    var property = path + "[" + index + "]", item = table[index++];
                    if (wrapped(item) !== item) accumulator[property] = item;
                    else reduce(property, accumulator, item);
                }
            } else accumulator[path] = table;
        } else {
            var empty = true;

            if (path) {
                for (var property in table) {
                    var item = table[property], property = path + "." + property, empty = false;
                    if (wrapped(item) !== item) accumulator[property] = item;
                    else reduce(property, accumulator, item);
                }
            } else {
                for (var property in table) {
                    var item = table[property], empty = false;
                    if (wrapped(item) !== item) accumulator[property] = item;
                    else reduce(property, accumulator, item);
                }
            }

            if (empty) accumulator[path] = table;
        }

        return accumulator;
    }
}(Array.isArray, Object));

</script>