.Net Core 2.1 - Read appsettings.json in javascript file

Question

I have a Web application in .net Core 2.1 using signalR. I need to pass HubUrl into custom javascript file. Is that possible in .net Core?

Sample of js code:

const connection = new signalR.HubConnectionBuilder()
.withUrl('http://localhost:5000/hub') //Here I need to read appSettings.json to get value from there
.configureLogging(signalR.LogLevel.Information)
.build();

Answer 1

appsettings.json located on server. So you need to add end-point to controller that returns needed value.

Controller:

public class MyController:Controller{
    private readonly IConfiguration configuration;

    public MyController(IConfiguration configuration){
         this.configuration = configuration;
    }

    [HTTPGet]
    public ActionResult GetConfigurationValue(string sectionName, string paramName){
        var parameterValue= configuration[$"{sectionName}:{paramName}"];
        return Json(new { parameter= parameterValue});
    }
}

Client side:

$.ajax({
    type:"GET",
    url: "/MyController/GetConfigurationValue"
    data:{
        sectionName = "MySection",
        paramName = "MyParameter"
    }
}).done(
    function(parameterValue){
        //do what you need
});

In appsettings.json:

{
    "MySection":{
        "MyParameter":"value that I want to get"
    }
}

Answer 2

In appsettings.json

"ApiUrls": {
    "commonUrl": "https://localhost:44348/api/"    
  }

In _Layout.cshtml

@using Microsoft.Extensions.Configuration
@inject IConfiguration Configuration

<script>      
        const commonUrl = @Json.Serialize(@Configuration.GetSection("ApiUrls").GetSection("commonUrl").Value)
</script>

now this will be like a global variable accessible to all js files