# Module Js

    module Js: sig .. end

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 : ('c -> 'a -> 'b) -> ('c, 'a -> 'b) 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.

    class type 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`.
Specification of Javascript regular arrays.

    class type ['a] js_array = object .. end

use `Js.array_get` and `Js.array_set` to access and set array elements.

    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`.

    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

    exception Error of error t

The `Error` exception wrap javascript exceptions when catched 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 -> 'a 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.

## 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.