Javascript JS授权/扩展aleady现有功能

如何向函数添加代码以保留其原有功能

SomeFunction = function () {
    someOtherFunction();
    return this.apply(this, arguments);
};

就这样

var delegate = functionToBeDelegated;
functionToBeDelegated = function () {

    //
    // Add functionality to the function
    //

    // run the old version of the function in native scope
    return delegate.apply(this, arguments);
};