Docs / API / Js

Js

The Js module mostly contains ReScript bindings to standard JavaScript APIs like console.log, or the JavaScript String, Date, and Promise classes.

It is meant as a zero-abstraction interop layer and directly exposes JavaScript functions as they are. If you can find your API in this module, prefer this over an equivalent Belt helper. For example, prefer Js.Array2 over Belt.Array

Argument Order

For historical reasons, some APIs in the Js namespace (e.g. Js.String) are using the data-last argument order whereas others (e.g. Js.Date) are using data-first.

For more information about these argument orders and the trade-offs between them, see this blog post.

Eventually, all modules in the Js namespace are going to be migrated to data-first though.

Js.Xxx2 Modules

Prefer Js.Array2 over Js.Array, Js.String2 over Js.String, etc. The latters are old modules.

t

Deprecated

This has been deprecated and will be removed in v13. Use the {..} type directly instead.

RESCRIPT

type t<'a> = 'a
  constraint 'a = {..}

JS object type

globalThis

Deprecated

RESCRIPT

let globalThis: t<{..}>

JS global object reference

null

Deprecated

RESCRIPT

@unboxed
type null<'a> = Js_null.t<'a> = Value('a) | @as(null) Null

undefined

Deprecated

This has been deprecated and will be removed in v13.

RESCRIPT

type undefined<'a> = Js_undefined.t<'a>

nullable

Deprecated

RESCRIPT

@unboxed
type nullable<'a> = Js_null_undefined.t<'a> =
  | Value('a)
  | @as(null) Null
  | @as(undefined) Undefined

null_undefined

Deprecated

RESCRIPT

type null_undefined<'a> = nullable<'a>

toOption

RESCRIPT

let toOption: nullable<'a> => option<'a>

undefinedToOption

Deprecated

RESCRIPT

let undefinedToOption: undefined<'a> => option<'a>

nullToOption

Deprecated

RESCRIPT

let nullToOption: null<'a> => option<'a>

isNullable

Deprecated

RESCRIPT

let isNullable: nullable<'a> => bool

import

Deprecated

RESCRIPT

let import: 'a => promise<'a>

testAny

Deprecated

RESCRIPT

let testAny: 'a => bool

The same as {!test} except that it is more permissive on the types of input

promise

Deprecated

This is deprecated and will be removed in v13. Use the promise type directly instead.

RESCRIPT

type promise<+'a, +'e>

The promise type, defined here for interoperation across packages.

null

Deprecated

RESCRIPT

let null: null<'a>

The same as empty in Js.Null. Compiles to null.

undefined

Deprecated

RESCRIPT

let undefined: undefined<'a>

The same as empty Js.Undefined. Compiles to undefined.

typeof

Deprecated

RESCRIPT

let typeof: 'a => string

typeof x will be compiled as typeof x in JS. Please consider functions in Js.Types for a type safe way of reflection.

log

Deprecated

RESCRIPT

let log: 'a => unit

Equivalent to console.log any value.

log2

Deprecated

RESCRIPT

let log2: ('a, 'b) => unit

log3

Deprecated

RESCRIPT

let log3: ('a, 'b, 'c) => unit

log4

Deprecated

RESCRIPT

let log4: ('a, 'b, 'c, 'd) => unit

logMany

Deprecated

RESCRIPT

let logMany: array<'a> => unit

A convenience function to console.log more than 4 arguments

eqNull

Deprecated

RESCRIPT

let eqNull: ('a, null<'a>) => bool

eqUndefined

Deprecated

RESCRIPT

let eqUndefined: ('a, undefined<'a>) => bool

eqNullable

Deprecated

RESCRIPT

let eqNullable: ('a, nullable<'a>) => bool

unsafe_lt

Deprecated

RESCRIPT

let unsafe_lt: ('a, 'a) => bool

unsafe_lt(a, b) will be compiled as a < b. It is marked as unsafe, since it is impossible to give a proper semantics for comparision which applies to any type

unsafe_le

Deprecated

RESCRIPT

let unsafe_le: ('a, 'a) => bool

unsafe_le(a, b) will be compiled as a <= b. See also Js.unsafe_lt.

unsafe_gt

Deprecated

RESCRIPT

let unsafe_gt: ('a, 'a) => bool

unsafe_gt(a, b) will be compiled as a > b. See also Js.unsafe_lt.

unsafe_ge

Deprecated

RESCRIPT

let unsafe_ge: ('a, 'a) => bool

unsafe_ge(a, b) will be compiled as a >= b. See also Js.unsafe_lt.