Is there a mechanism and possibility to modify the js script on the fly? The script is in the wwwroot folder, you need to somehow inject variables into it. The variant with cshtml and other standard methods are not suitable. Thank.

Example: in wwwroot is file.js with content

{ myVar: null }

It is necessary that when you return the content is replaced by

 { myVar: "someValueFromBackEnd"}
  • one
    It is possible in more detail with the example of the script and what I want to get in the end? And why the option with cshtml does not suit? - chromigo
  • @chromigo, added an example. For the reason that we do not have cshtml, but there is a generated front webcam. - Ssss
  • if the data is dynamically received from the server, then just make an ajax request to the backend and pull the necessary data from there. If you do not want to send requests, this is not a very simple case. If these are just fixed values ​​from the config that do not change or change hands and rarely, you can try to parse the bundle on the backend (and if it regenerates, parse again and change the value). But parsing this bundle may not be very easy) - chromigo
  • I can offer you the option with httpHandler, just add <httpHandlers><add verb="*" path="*.js" type="YourJsHandler" /> `read the file yourself, rework as you like. Is this mechanism for you to show? Here is the "scratch" is msdn.microsoft.com/ru-ru/library/ms228090(v=vs.100).aspx - nick_n_a
  • @nick_n_a is an option for non-core - PashaPash ♦

2 answers 2

In the .net core, the so-called middleware processor and the contents of the wwwroot folder in the project should not be used to process any request. To do this, you connect one of the extensions, for example, UseStaticFiles in your startup.cs. If there is middleware, then there is an output stream that can be modified at its discretion before sending to the client (for example, this is how middleware works by dynamically compressing the response).

All you need to do is correctly replace the outgoing stream provided by the .net core infrastructure with the class you have inherited from the standard class Stream, get all the data (in your case it is a js file), find all the places where a replacement is needed (mark them with a unique combination, for example _____please_replace_me_1_____ ), substitute your values ​​and send the result to the original stream (which you prudently saved in the class instance of your stream).

It sounds simple, but in fact you need to take into account many details that are not so obvious. The best solution is to see how the middleware I wrote is written by Microsoft itself (since recently the source can be found on github, for example, https://github.com/aspnet/StaticFiles , and also here https://github.com/aspnet/BasicMiddleware /tree/dev/src/Microsoft.AspNetCore.ResponseCompression ).

After examining the sources, you can try to create your own solution, which I did https://github.com/bopohaa/ResponseProxy This extension allows you to replace one word in a static js file before giving it to the client.

I hope I helped you.

    You are trying to make the dynamics of static, it will lead to crutches like rewriting the contents of static on the fly.

    There is a standard solution:

    1. Instead of hardcode values ​​- describe in your static ajax call backend
    2. In the controller backend give JsonResult
    3. On the frontend, this Json is parsed (most likely your favorite framework itself will parse it)

    As an option, crutch:

    1. To prescribe on the page the path not to the file, but to the MVC Action.
    2. In the action, read the real file into a string.
    3. Replace all you need.
    4. Give the result of the replacement as a ContentResult with the desired content type.
    • Sometimes an additional request is too expensive for the application - Nikolay
    • @Nikolay yes, but this is a choice between - 1) to make one mandatory thick request for a large variable script at each visit, replacing the value in it. 2) fill in a thick immutable script on cdn, aggressively cache it on the client, and when entering do one small query after dynamics. Those. it is clear that there are situations when 1 is more profitable (the client visits the application exactly once, never returns, and does nothing in the application). But in other cases it is more profitable 2. - PashaPash ♦
    • @Nikolay is another matter that in (1) the 100% relevance of the dynamics is usually not important, and the more profitable is the mixed version - stuffing the updated static on cdn on a schedule. Some porn sites do this - and they have absolutely amazing loading times. - PashaPash ♦