Constants

You can use the const keyword to declare constant values. These values cannot be changed at runtime. Constant references will be inlined at compile-time, which is very efficient (similar to how enums work).

NOTE: These are not to be confused with the conditional compile #const statements, which are a totally different thing.

Basic usage

Consts can be defined at the root level of files, and are scoped the same way as functions.

const GREETING_MESSAGE = "Hello world"
sub main()
    print GREETING_MESSAGE
end sub

transpiles to

sub main()
    print "Hello world"
end sub

Namespaced Consts

Consts can be defined within namespaces, and accessed like a property.

namespace networking
    const BASE_URL = "https://your-app.com/api/v1"
    sub printBaseUrl()
		'namespace-relative access is allowed
        print BASE_URL
    end sub
end namespace
sub main()
    print networking.BASE_URL
end sub

transpiles to

sub networking_printBaseUrl()
    'namespace-relative access is allowed
    print "https://your-app.com/api/v1"
end sub

sub main()
    print "https://your-app.com/api/v1"
end sub

Complex objects

Constants can contain complex objects or arrays as well, but keep in mind that these are inlined at compile-time, so it is not recommended to reach into these objects for specific values all the time.

non-primitive const values will be wrapped with parentheses when transpiled.

namespace networking
	const HEADERS = {
		"Authorization": "Basic",
		"Access-Control-Allow-Credentials": "true"
	}
	const METHODS = [
	    "GET",
	    "POST",
	    "PUT",
	    "DELETE"
	]
end namespace
sub main()
    print networking.HEADERS
    print networking.METHODS
end sub

Transpiled:

sub main()
    print ({
        "Authorization": "Basic"
        "Access-Control-Allow-Credentials": "true"
    })
    print ([
        "GET"
        "POST"
        "PUT"
        "DELETE"
    ])
end sub

Using constants as computed associative array keys

String constants can be used as computed keys in associative array literals. See Computed Property Names for full details.

Referencing other constants

Constants can reference other constants (as long as there is no circular reference). You can even use template strings!

const BASE_URL = "https://api.domain.com"
const LOGIN_PATH = "/login"

const LOGIN_URL = BASE_URL + LOGIN_PATH

const ERROR_URL = `${BASE_URL}/some/error`
sub main()
    print LOGIN_URL
    print ERROR_URL
end sub

transpiles to

sub main()
    print ("https://api.domain.com" + "/login")
    print ((bslib_toString("https://api.domain.com") + "/some/error"))
end sub