function executeFunctionByName(functionName, context /*, args*/) {
    var args = Array.prototype.slice.call(arguments).splice(2);
    var namespaces = functionName.split(".");
    var func = namespaces.pop();
    for(var i = 0; i < namespaces.length; i++) {
      context = context[namespaces[i]];
    }
    return context[func].apply(this, args);
  }
Thanks to Jason Bunting via StackOverflow.com

http://stackoverflow.com/questions/359788/how-to-execute-a-javascript-function-when-i-have-its-name-as-a-string#answer-359910
Short link: http://tinyurl.com/executeFunctionByName