Module Brr.Console

Browser console.

See Console. Take a few minutes to understand this.

type t

The type for console objects. See G.console for the global console object.

val get : unit -> t

get () is the console object on which the functions below act. Initially this is G.console.

val set : t -> unit

set o sets the console object to o.

val clear : unit -> unit

clear () clears the console.

Log functions

type msg =
| ([]) : msg
| (::) : 'a * msg -> msg

The type for log messages.

type 'a msgr = 'a -> msg

The type for functions turning values of type 'a into log messages.

val msg : 'a msgr

msg v is [v].

type log = msg -> unit

The type for log functions.

Log messages rebind OCaml's list syntax. This allows to write heterogeneous logging statements concisely.

let () = Console.(log [1; 2.; true; Jv.true'; str "🐫"; G.navigator])

The console logs JavaScript values. For OCaml values this means that their js_of_ocaml representation is logged; see the FFI manual for details. Most OCaml values behind Brr types are however direct JavaScript values and logging them as is will be valuable. For other values you can use the str function which invokes the JavaScript toString method on the value. It works on OCaml strings and is mostly equivalent and shorter than calling Jstr.v before logging them.

In the JavaScript console API, if the first argument is a JavaScript string it can have formatting specifications. Just remember this should be a JavaScript string, so wrap OCaml literals by str or Jstr.v:

let () = Console.(log [str "This is:\n%o\n the navigator"; G.navigator])
val str : 'a -> Jstr.t

str v is the result of invoking the JavaScript toString method on the representation of v. If v is Jv.null and Jv.undefined a string representing them is directly returned.

Result logging

val log_result : ?⁠ok:'a msgr -> ?⁠error:'b msgr -> ('a'b) Stdlib.result -> ('a'b) Stdlib.result
val log_if_error : ?⁠l:log -> ?⁠error_msg:'b msgr -> use:'a -> ('a'b) Stdlib.result -> 'a

log_if_error ~l ~error_msg ~use r is v if r is Ok v and use if r is Error e. In this case e is logged with l (defaults to error) and error_msg (defaults to str e).

val log_if_error' : ?⁠l:log -> ?⁠error_msg:'b msgr -> use:'a -> ('a'b) Stdlib.result -> ('a'b) Stdlib.result

log_if_error' is log_if_error wrapped by Result.ok.

Levelled logging

val log : log

log m logs m with no specific level.

val trace : log

trace m logs m with no specific level but with a stack trace, like error and warn do.

val error : log

error m logs m with level error.

val warn : log

warn m logs m with level warn.

val info : log

warn m logs m with level info.

val debug : log

debug m logs m with level debug.

Asserting and dumping

val assert' : bool -> log

assert' c m asserts c and logs m with a stack trace iff c is false.

val dir : 'a -> unit

dir o logs a listing of the properties of the object othis explains the difference with Console.(log [o]).

val table : ?⁠cols:Jstr.t list -> 'a -> unit

table v outputs v as tabular data. If cols is specified only the specified properties are printed.


val group : ?⁠closed:bool -> log

group ~closed msg logs msg and pushes a new inline group in the console. This indents messages until group_end is called. If closed is true (defaults to false) the group's content is hidden behind a disclosure button.

val group_end : unit -> unit

group_end () pops the last inline group.


val count : Jstr.t -> unit

count label logs label with the number of times count label was called.

val count_reset : Jstr.t -> unit

count_reset label resets the counter for count label.


val time : Jstr.t -> unit

time label starts a timer named label.

val time_log : Jstr.t -> log

time_log label msg reports the timer value of label with msg appended to the report.

val time_end : Jstr.t -> unit

time_end label ends the timer named label.


val profile : Jstr.t -> unit

profile label starts a new profile labelled label.

val profile_end : Jstr.t -> unit

profile_end label ends ends the new profile labelled label.

val time_stamp : Jstr.t -> unit

time_stamp label adds a marker labeled by label in the waterfall view.