Have you ever wanted to post from your javascript program to a Rails app so that the params are available to your application in a properly nested hash? Prototype makes this easy for form elements with it's Form Serializer, but it makes no provision for standard javascript objects.

Suffer no longer. With the following code you can serialize arbitrarily nested objects (eg, the sort of thing you get when you parse a JSON statement), so that it is ready to be posted via http to a Rails app.

The original Rails recursive Javascript object serializer.

var serializer = {
 
  serialize : function(object) {
    var values = []; 
    var prefix = '';
    
    values = this.recursive_serialize(object, values, prefix);
    
    param_string = values.join('&');
    return param_string;
  },
  
  recursive_serialize : function(object, values, prefix) {
    for (key in object) {
      if (typeof object[key] == 'object') {
        
        if (prefix.length > 0) {
          prefix += '['+key+']';         
        } else {
          prefix += key;
        }
        
        values = this.recursive_serialize(object[key], values, prefix);
        
        prefixes = prefix.split('[');
        
        if (prefixes.length > 1) {
          prefix = prefixes.slice(0,prefixes.length-1).join('[');
        } else {
          prefix = prefixes[0];
        }
        
      } else {
        value = encodeURIComponent(object[key]);
        if (prefix.length > 0) {
          prefixed_key = prefix+'['+key+']'          
        } else {
          prefixed_key = key
        }
        prefixed_key = encodeURIComponent(prefixed_key);
        if (value) values.push(prefixed_key + '=' + value);
      }
    }
    return values;
  }
}

Usage:

payload = new Object;
payload.comment = new Object;
payload.comment.title = "The Title";
payload.comment.body = "The body of the post.";
post_string = serializer.serialize(payload);

Result:

comment%5Btitle%5D=The%20Title&comment%5Bbody%5D=The%20body%20of%20the%20post.

Which gives you this in Rails:

params[:comment] #=>
{:title => "The Title", :body => "The body of the post."}