CODE EXAMPLE FOR JAVASCRIPT

why can i put comments in some json files

In some files the option for checking comments is off by default 
(tsconfig, tslint and eslint configs), as corresponding tools allow comments in
JSON (this is hardcoded). 

So IDEs recognize this and allow you to add comments even if standard 
doesnt allow.

Otherwise use:
{
	"_comment": "comment text goes here...",
    "name": "your-app-name",
    ...
}