Module `Js_of_ocaml.Js`

Javascript binding

This module provides types and functions to interoperate with Javascript values, and gives access to Javascript standard objects.

Dealing with `null` and `undefined` values.

type +'a opt: Type of possibly null values.

type +'a optdef: Type of possibly undefined values.

val null : 'a opt: The null value.

val some : 'a -> 'a opt: Consider a value into a possibly null value.

val undefined : 'a optdef: The undefined value

val def : 'a -> 'a optdef: Consider a value into a possibly undefined value.

module type OPT = sig ... end: Signatures of a set of standard functions for manipulating optional values.

module Opt : OPT with type 'a t = 'a opt: Standard functions for manipulating possibly null values.

module Optdef : OPT with type 'a t = 'a optdef: Standard functions for manipulating possibly undefined values.

Types for specifying method and properties of Javascript objects

type +'a t: Type of Javascript objects. The type parameter is used to specify more precisely an object.

type +'a meth: Type used to specify method types: a Javascript object <m : t1 -> t2 -> ... -> tn -> t Js.meth> Js.t has a Javascript method m expecting n arguments of types t1 to tn and returns a value of type t.

type +'a gen_prop: Type used to specify the properties of Javascript objects. In practice you should rarely need this type directly, but should rather use the type abbreviations below instead.

type 'a readonly_prop = < get : 'a; > gen_prop: Type of read-only properties: a Javascript object <p : t Js.readonly_prop> Js.t has a read-only property p of type t.

type 'a writeonly_prop = < set : 'a -> unit; > gen_prop: Type of write-only properties: a Javascript object <p : t Js.writeonly_prop> Js.t has a write-only property p of type t.

type 'a prop = < get : 'a; set : 'a -> unit; > gen_prop: Type of read/write properties: a Javascript object <p : t Js.writeonly_prop> Js.t has a read/write property p of type t.

type 'a optdef_prop = < get : 'a optdef; set : 'a -> unit; > gen_prop: Type of read/write properties that may be undefined: you can set them to a value of some type t, but if you read them, you will get a value of type t optdef (that may be undefined).

Object constructors

type +'a constr: A value of type (t1 -> ... -> tn -> t Js.t) Js.constr is a Javascript constructor expecting n arguments of types t1 to tn and returning a Javascript object of type t Js.t. Use the syntax extension jsnew c (e1, ..., en) to build an object using constructor c and arguments e1 to en.

Callbacks to OCaml

type (-'a, +'b) meth_callback: Type of callback functions. A function of type (u, t1 -> ... -> tn -> t) meth_callback can be called from Javascript with this bound to a value of type u and up to n arguments of types t1 to tn. The system takes care of currification, so less than n arguments can be provided. As a special case, a callback of type (t, unit -> t) meth_callback can be called from Javascript with no argument. It will behave as if it was called with a single argument of type unit.

type 'a callback = (unit, 'a) meth_callback: Type of callback functions intended to be called without a meaningful this implicit parameter.

val wrap_callback : ('a -> 'b) -> ('c, 'a -> 'b) meth_callback: Wrap an OCaml function so that it can be invoked from Javascript.

val wrap_meth_callback : ('b -> 'a) -> ('b, 'a) meth_callback: Wrap an OCaml function so that it can be invoked from Javascript. The first parameter of the function will be bound to the value of the this implicit parameter.

Javascript standard objects

val _true : bool t: Javascript true boolean.

val _false : bool t: Javascript false boolean.

type match_result_handle: A handle to a match result. Use function Js.match_result to get the corresponding MatchResult object. (This type is used to resolved the mutual dependency between string and array type definitions.)

type string_array: Opaque type for string arrays. You can get the actual Array object using function Js.str_array. (This type is used to resolved the mutual dependency between string and array type definitions.)

class type js_string = object ... end: Specification of Javascript string objects.

and regExp = object ... end: Specification of Javascript regular expression objects.

class type string_constr = object ... end: Specification of the string constructor, considered as an object.

val string_constr : string_constr t: The string constructor, as an object.

val regExp : (js_string t -> regExp t) constr: Constructor of RegExp objects. The expression jsnew regExp (s) builds the regular expression specified by string s.

val regExp_withFlags : (js_string t -> js_string t -> regExp t) constr: Constructor of RegExp objects. The expression jsnew regExp (s, f) builds the regular expression specified by string s using flags f.

val regExp_copy : (regExp t -> regExp t) constr: Constructor of RegExp objects. The expression jsnew regExp (r) builds a copy of regular expression r.

class type 'a js_array = object ... end: Specification of Javascript regular arrays. Use Js.array_get and Js.array_set to access and set array elements.

val object_keys : 'a t -> js_string t js_array t: Returns jsarray containing keys of the object as Object.keys does.

val array_empty : 'a js_array t constr: Constructor of Array objects. The expression jsnew array_empty () returns an empty array.

val array_length : (int -> 'a js_array t) constr: Constructor of Array objects. The expression jsnew array_length (l) returns an array of length l.

val array_get : 'a js_array t -> int -> 'a optdef: Array access: array_get a i returns the element at index i of array a. Returns undefined if there is no element at this index.

val array_set : 'a js_array t -> int -> 'a -> unit: Array update: array_set a i v puts v at index i in array a.

val array_map : ('a -> 'b) -> 'a js_array t -> 'b js_array t: Array map: array_map f a is a##map(wrap_callback (fun elt idx arr -> f elt)).

val array_mapi : (int -> 'a -> 'b) -> 'a js_array t -> 'b js_array t: Array mapi: array_mapi f a is a##map(wrap_callback (fun elt idx arr -> f idx elt)).

class type match_result = object ... end: Specification of match result objects

val str_array : string_array t -> js_string t js_array t: Convert an opaque string_array t object into an array of string. (Used to resolved the mutual dependency between string and array type definitions.)

val match_result : match_result_handle t -> match_result t: Convert a match result handle into a MatchResult object. (Used to resolved the mutual dependency between string and array type definitions.)

class type number = object ... end: Specification of Javascript number objects.

val number_of_float : float -> number t: Conversion of OCaml floats to Javascript number objects.

val float_of_number : number t -> float: Conversion of Javascript number objects to OCaml floats.

class type date = object ... end: Specification of Javascript date objects.

val date_now : date t constr: Constructor of Date objects: jsnew date_now () returns a Date object initialized with the current date.

val date_fromTimeValue : (float -> date t) constr: Constructor of Date objects: jsnew date_fromTimeValue (t) returns a Date object initialized with the time value t.

val date_month : (int -> int -> date t) constr: Constructor of Date objects: jsnew date_fromTimeValue (y, m) returns a Date object corresponding to year y and month m.

val date_day : (int -> int -> int -> date t) constr: Constructor of Date objects: jsnew date_fromTimeValue (y, m, d) returns a Date object corresponding to year y, month m and day d.

val date_hour : (int -> int -> int -> int -> date t) constr: Constructor of Date objects: jsnew date_fromTimeValue (y, m, d, h) returns a Date object corresponding to year y to hour h.

val date_min : (int -> int -> int -> int -> int -> date t) constr: Constructor of Date objects: jsnew date_fromTimeValue (y, m, d, h, m') returns a Date object corresponding to year y to minute m'.

val date_sec : (int -> int -> int -> int -> int -> int -> date t) constr: Constructor of Date objects: jsnew date_fromTimeValue (y, m, d, h, m', s) returns a Date object corresponding to year y to second s.

val date_ms : (int -> int -> int -> int -> int -> int -> int -> date t) constr: Constructor of Date objects: jsnew date_fromTimeValue (y, m, d, h, m', s, ms) returns a Date object corresponding to year y to millisecond ms.

class type date_constr = object ... end: Specification of the date constructor, considered as an object.

val date : date_constr t: The date constructor, as an object.

class type math = object ... end: Specification of Javascript math object.

val math : math t: The Math object

class type error = object ... end: Specification of Javascript error object.

val error_constr : (js_string t -> error t) constr: Constructor of Error objects: jsnew error_constr (msg) returns an Error object with the message msg.

val string_of_error : error t -> string
val raise_js_error : error t -> 'a

exception Error of error t: The Error exception wrap javascript exceptions when caught by OCaml code. In case the javascript exception is not an instance of javascript Error, it will be serialized and wrapped into a Failure exception.

class type json = object ... end: Specification of Javascript JSON object.

val _JSON : json t: JSON object

Standard Javascript functions

val decodeURI : js_string t -> js_string t: Decode a URI: replace by the corresponding byte all escape sequences but the ones corresponding to a URI reserved character and convert the string from UTF-8 to UTF-16.

val decodeURIComponent : js_string t -> js_string t: Decode a URIComponent: replace all escape sequences by the corresponding byte and convert the string from UTF-8 to UTF-16.

val encodeURI : js_string t -> js_string t: Encode a URI: convert the string to UTF-8 and replace all unsafe bytes by the corresponding escape sequence.

val encodeURIComponent : js_string t -> js_string t: Same as encodeURI, but also encode URI reserved characters.

val escape : js_string t -> js_string t: Escape a string: unsafe UTF-16 code points are replaced by 2-digit and 4-digit escape sequences.

val unescape : js_string t -> js_string t: Unescape a string: 2-digit and 4-digit escape sequences are replaced by the corresponding UTF-16 code point.

val isNaN : 'a -> bool
val parseInt : js_string t -> int
val parseFloat : js_string t -> float

Conversion functions between Javascript and OCaml types

val bool : bool -> bool t: Conversion of booleans from OCaml to Javascript.

val to_bool : bool t -> bool: Conversion of booleans from Javascript to OCaml.

val string : string -> js_string t: Conversion of strings from OCaml to Javascript. (The OCaml string is considered to be encoded in UTF-8 and is converted to UTF-16.)

val to_string : js_string t -> string: Conversion of strings from Javascript to OCaml.

val array : 'a array -> 'a js_array t: Conversion of arrays from OCaml to Javascript.

val to_array : 'a js_array t -> 'a array: Conversion of arrays from Javascript to OCaml.

val bytestring : string -> js_string t: Conversion of strings of bytes from OCaml to Javascript. (Each byte will be converted in an UTF-16 code point.)

val to_bytestring : js_string t -> string: Conversion of strings of bytes from Javascript to OCaml. (The Javascript string should only contain UTF-16 code points below 255.)

Convenience coercion functions

val coerce : 'a -> ('a -> 'b Opt.t) -> ('a -> 'b) -> 'b: Apply a possibly failing coercion function. coerce v c f attempts to apply coercion c to value v. If the coercion returns null, function f is called.

val coerce_opt : 'a Opt.t -> ('a -> 'b Opt.t) -> ('a -> 'b) -> 'b

Apply a possibly failing coercion function. coerce_opt v c f attempts to apply coercion c to value v. If v is null or the coercion returns null, function f is called. Typical usage is the following:

Js.coerce_opt (Dom_html.document##getElementById id)
Dom_html.CoerceTo.div (fun _ -> assert false)

Type checking operators.

val typeof : _ t -> js_string t: Returns the type of a Javascript object.

val instanceof : _ t -> _ constr -> bool: Tests whether a Javascript object is an instance of a given class.

Debugging operations.

val debugger : unit -> unit: Invokes any available debugging functionality. If no debugging functionality is available, it has no effect. In practice, it will insert a "debugger;" statement in the generated javascript.

Export functionality.

Export values to module.exports if it exists or to the global object otherwise.

val export : string -> 'a -> unit: export name value export name

val export_all : 'a t -> unit

export_all obj export every key of obj object.

export_all
  object%js
    method add x y = x +. y
    method abs x = abs_float x
    val zero = 0.
  end

Unsafe operations.

module Unsafe : sig ... end: Unsafe Javascript operations

Deprecated functions and types.

val float : float -> float: Conversion of OCaml floats to Javascript numbers.

val to_float : float -> float: Conversion of Javascript numbers to OCaml floats.

type float_prop = float prop: Type of float properties.