stringifyCyclicJSON.js

function stringifyCyclicJSON(sourceObject, maxDepth = 5)
{
    var knownObjects = {};
    var jsonString = '';
    recStringifyObject(sourceObject, '', 1, 'root');
    return jsonString;

    function recStringifyObject(currentObject, indent, level, path)
    {
        var isArray = (currentObject instanceof Array);
        var subIndent = indent + '\t';
        var i = 0;
        jsonString += (isArray ? '[' : '{');
        if (isArray)
        {
            for (; i < currentObject.length; i++)
            {
                doSingleStringify(i, '');
            }
        }
        else
        {
            for (var key in currentObject)
            {
                if (currentObject[key] !== undefined)
                {
                    doSingleStringify(key, '"' + key + '": ');
                    i++;
                }
            }
        }
        jsonString += (i > 0 ? '\n' + indent : ' ') + (isArray ? ']' : '}');

        function doSingleStringify(key, addBefore)
        {
            var value = currentObject[key];
            jsonString += '\n'
                + subIndent
                + (i > 0 ? ', ' : '')
                + addBefore;
            if (typeof value == 'object')
            {
                // first search in known Objects
                var found = false;
                for (var pathKey in knownObjects)
                {
                    if (knownObjects[pathKey] == value)
                    {
                        jsonString += '"[' + pathKey + ']"';
                        found = true;
                    }
                }
                if (!found)
                {
                    var newPath = path + (isArray ? '[' + key + ']' : '.' + key);
                    knownObjects[newPath] = value;
                    if (level < maxDepth)
                    {
                        recStringifyObject(value, subIndent, level + 1, newPath);
                    }
                    else
                    {
                        jsonString += '"[' + (value instanceof Array ? 'Array' : 'Object') + ']"';
                    }
                }
            }
            else if (typeof value == 'function')
            {
                jsonString += '"[Function]"';
            }
            else
            {
                jsonString += JSON.stringify(value);
            }
        }
    }
}