lib/jsonscript.js
function addExecutor(name, executor) {
  if (this._executors[name]) throw new Error('executor "' + name + '" is already defined');
  this._executors[name] = executor;
}
function addExecutor(name, executor) {
  if (this._executors[name]) throw new Error('executor "' + name + '" is already defined');
  this._executors[name] = executor;
}
function addExecutor ( name , executor ) { if ( this . _executors [ name ] ) throw new Error ( 'executor "' + name + '" is already defined' ) ; this . _executors [ name ] = executor ; }
add external executor to JSONScript interpreter
@this  JSONScript
@param {String}          name     executor name to use in $exec keyword
@param {Object|Function} executor executor object or function
add external executor to JSONScript interpreter