Concatenate value from the same JSON - json

Question

I'm working on a configuration service in Angular 2 which simply retrieve the content of my JSON file defined above.
{
"application": {
"baseUrl": "http://localhost:1691/",
"environment": "dev"
},
"error": {
"title": "Title Error",
"description": "Error message"
}
}
I would like now, to add a properties using the baseUrl and concatenate a string after, I tried with this but it's obviously not working:
"baseApiUrl": baseUrl + "api/",
Is my requirement possible to do or have I to do it manually in my code?
My dream result would be something like this:
{
"application": {
"baseUrl": "http://localhost:1691/",
"baseApiUrl": baseUrl + "api/",
"environment": "dev"
},
"error": {
"title": "Title Error",
"description": "Error message"
}
}

Answer 1

My dream result would be something like this
JSON has no mechanism for referring to other parts of the structure like that. JSON is a very simple data-only format defined here.
Assuming you have that JSON as a string, you parse it, then add a property to the application object:
var configuration = JSON.parse(configurationString);
configuration.application.baseApiUrl = configuration.application.baseUrl + "api/";
Then depending on what you need to do with it, you either use configuration (the object), or turn it back into a string via JSON.stringify, or whatever else you need to do.