python - sandwich pattern in javascript code

Question

Apologize if the title of the question is misleading. Actually I am looking for the javascript equivalent of the following python code:

## python code
def call_with_context(fn, *args):
  ## code to create context, e.g. profiling, db.connect, or drawing context store stack
  fn(*args)
  ## code to close context 

This implements the similiar functionality as the "with statement" in python, which implements the aspect-oriented paradigm.

So my question is what is the javascript way of doing such things? I have seen some code using Array.prototype.slice(arguments, 1) to do so, but I don't know if this is a common pattern in javascript, or there are better patterns supported in javascript (e.g. by closure) so ppl don't really do that. Pls also correct me if I am using the wrong keywords, because I really dont know how to refer to my problem with a better name than sandwich.

EDT 1: And I appreciate if someone can explain how to return the result of fn(*args) from inside the wrapper call_with_context. thanks!

Answer 1

It sounds like you want to call a method with specific context.

In js, you would typically do...

function someFunction( fn, context ) {
   fn.call( context );
}

var Button = {
   isClicked: false
};
someFunction(function () {
   // this === Button
   this.isClicked = true;
}, Button );

now the this keyword inside of fn will represent the context passed into the method someFunction. This sort of pattern is done quite often. Especially with the callbacks.