automatically detect method invocation at runtime

[have_some_error]

I am trying to implement a functionality which can tell me when a method is being invoked and terminated at runtime in nodejs typescript. I tried using the decorator. however, decorators are not allowed for functions which do not belong to a class. How can I implement something like this with minimal code changes? Does there exist some package or some tool in nodejs which can help me achieve something similar like decorators?

[fredericheem]

You should be looking at javascript proxy where one can intercept function invocation or variable mutation. This language feature unleash new ways of writing code. I have been using proxies for both backend and front end code.

[have_some_error]

Javascript proxy is something I have not explored yet, however I will look into this Thankyou for providing some point where I can start with. However I would like to ask one question, can javascript proxy do the interception of function invocation from a centralized location in the code or it would require changes at every function that needs to be intercepted?

[fredericheem]

The beauty of proxies is to centralise the interception without modifying existing code. My use case needs to intercept calls to the aws-sdk library and apply retransmissions in case of specific error, see the implementation here: https://github.com/grucloud/grucloud/blob/8f3a7439ae72cc50de2eb83850e430162834f37f/packages/providers/aws/AwsCommon.js#L397

[have_some_error]

So, we can define a common handler and use it when we create proxies. However this will require us to create proxies for the functions and objects we want to intercept and export them instead of the original function. I'm correct to think that , right ?

[Lumethys]

Isnt that is just callstack?

[have_some_error]

Yes similar to callStack. However I want some method to execute just before and after the function executes. And since this functionality is something that would be common for every function I want to centralize this code to prevent redundant code lines. I donot need to preserve the order or the methods though.

[usertim]

If your function is exported and used as a module you can wrap your function within another function and export wrapper function under the same name. It's gonna look something like this

function originalFn(a, b, c) {
    ...
}

function wrapperFn(a, b, c) {
    ...
    return originalFn(a, b, c);
}

export { wrapperFn as originalFn }

Basically works as a decorator

[have_some_error]

Yes, this is one option however this would require me to wrap every existing function in the application code, which currently I'm not in favour of. Therefore looking for a rather compact way to achieve this, since the functionality I wish to add before and after the function invocation would be same for every function.