This Module implements types and macros to facilitate the wrapping of, and interaction with JavaScript libraries. Using the provided types JsObject and JsAssoc together with the provided macros allows for smoother interfacing with JavaScript, allowing for example quick and easy imports of JavaScript variables:

Example:

import std/jsffi
# Here, we are using jQuery for just a few calls and do not want to wrap the
# whole library:

# import the document object and the console
var document {.importc, nodecl.}: JsObject
var console {.importc, nodecl.}: JsObject
# import the "$" function
proc jq(selector: JsObject): JsObject {.importjs: "$$(#)".}

# Use jQuery to make the following code run, after the document is ready.
# This uses an experimental `.()` operator for `JsObject`, to emit
# JavaScript calls, when no corresponding proc exists for `JsObject`.
proc main =
  jq(document).ready(proc() =
    console.log("Hello JavaScript!")
  )

Imports

macros, tables

Types

js = JsObject: Source Edit
JsAssoc[K; V] = ref object of JsRoot: Statically typed wrapper around a JavaScript object. Source Edit
JsError {.importc: "Error".} = object of JsRoot message*: cstring: Source Edit
JsEvalError {.importc: "EvalError".} = object of JsError: Source Edit
JsKey = concept atypeof(T) cstring.toJsKey(T) is T: Source Edit
JsObject = ref object of JsRoot: Dynamically typed wrapper around a JavaScript object. Source Edit
JsRangeError {.importc: "RangeError".} = object of JsError: Source Edit
JsReferenceError {.importc: "ReferenceError".} = object of JsError: Source Edit
JsSyntaxError {.importc: "SyntaxError".} = object of JsError: Source Edit
JsTypeError {.importc: "TypeError".} = object of JsError: Source Edit
JsURIError {.importc: "URIError".} = object of JsError: Source Edit

Vars

jsArguments: JsObject: JavaScript's arguments pseudo-variable. Source Edit
jsDirname: cstring: JavaScript's __dirname pseudo-variable. Source Edit
jsFilename: cstring: JavaScript's __filename pseudo-variable. Source Edit
jsNull: JsObject: JavaScript's null literal. Source Edit
jsUndefined: JsObject: JavaScript's undefined literal. Source Edit

Procs

proc `%=`(x, y: JsObject): JsObject {.importjs: "(# %= #)", discardable, ...raises: [], tags: [].}: Source Edit
proc `%`(x, y: JsObject): JsObject {.importjs: "(# % #)", ...raises: [], tags: [].}: Source Edit
proc `&`(a, b: cstring): cstring {.importjs: "(# + #)", ...raises: [], tags: [].}: Concatenation operator for JavaScript strings. Source Edit
proc `**`(x, y: JsObject): JsObject {.importjs: "((#) ** #)", ...raises: [], tags: [].}: Source Edit
proc `*=`(x, y: JsObject): JsObject {.importjs: "(# *= #)", discardable, ...raises: [], tags: [].}: Source Edit
proc `*`(x, y: JsObject): JsObject {.importjs: "(# * #)", ...raises: [], tags: [].}: Source Edit
proc `++`(x: JsObject): JsObject {.importjs: "(++#)", ...raises: [], tags: [].}: Source Edit
proc `+=`(x, y: JsObject): JsObject {.importjs: "(# += #)", discardable, ...raises: [], tags: [].}: Source Edit
proc `+`(x, y: JsObject): JsObject {.importjs: "(# + #)", ...raises: [], tags: [].}: Source Edit
proc `--`(x: JsObject): JsObject {.importjs: "(--#)", ...raises: [], tags: [].}: Source Edit
proc `-=`(x, y: JsObject): JsObject {.importjs: "(# -= #)", discardable, ...raises: [], tags: [].}: Source Edit
proc `-`(x, y: JsObject): JsObject {.importjs: "(# - #)", ...raises: [], tags: [].}: Source Edit
proc `/=`(x, y: JsObject): JsObject {.importjs: "(# /= #)", discardable, ...raises: [], tags: [].}: Source Edit
proc `/`(x, y: JsObject): JsObject {.importjs: "(# / #)", ...raises: [], tags: [].}: Source Edit
proc `<=`(x, y: JsObject): JsObject {.importjs: "(# <= #)", ...raises: [], tags: [].}: Source Edit
proc `<`(x, y: JsObject): JsObject {.importjs: "(# < #)", ...raises: [], tags: [].}: Source Edit
proc `==`(x, y: JsRoot): bool {.importjs: "(# === #)", ...raises: [], tags: [].}: Compares two JsObjects or JsAssocs. Be careful though, as this is comparison like in JavaScript, so if your JsObjects are in fact JavaScript Objects, and not strings or numbers, this is a comparison of references. Source Edit
proc `>=`(x, y: JsObject): JsObject {.importjs: "(# >= #)", ...raises: [], tags: [].}: Source Edit
proc `>`(x, y: JsObject): JsObject {.importjs: "(# > #)", ...raises: [], tags: [].}: Source Edit
proc `[]=`[K: JsKey; V](obj: JsAssoc[K, V]; field: K; val: V) {. importjs: "#[#] = #", ...raises: [], tags: [].}: Sets the value of a property of name field in a JsAssoc obj to v. Source Edit
proc `[]=`[T](obj: JsObject; field: cstring; val: T) {.importjs: "#[#] = #", ...raises: [], tags: [].}: Sets the value of a property of name field in a JsObject obj to v. Source Edit
proc `[]=`[T](obj: JsObject; field: int; val: T) {.importjs: "#[#] = #", ...raises: [], tags: [].}: Sets the value of a property of name field in a JsObject obj to v. Source Edit
proc `[]=`[V](obj: JsAssoc[cstring, V]; field: string; val: V): Source Edit
proc `[]`(obj: JsObject; field: cstring): JsObject {.importjs: "#[#]", ...raises: [], tags: [].}: Returns the value of a property of name field from a JsObject obj. Source Edit
proc `[]`(obj: JsObject; field: int): JsObject {.importjs: "#[#]", ...raises: [], tags: [].}: Returns the value of a property of name field from a JsObject obj. Source Edit
proc `[]`[K: JsKey; V](obj: JsAssoc[K, V]; field: K): V {.importjs: "#[#]", ...raises: [], tags: [].}: Returns the value of a property of name field from a JsAssoc obj. Source Edit
proc `[]`[V](obj: JsAssoc[cstring, V]; field: string): V: Source Edit
proc `and`(x, y: JsObject): JsObject {.importjs: "(# && #)", ...raises: [], tags: [].}: Source Edit
proc `in`(x, y: JsObject): JsObject {.importjs: "(# in #)", ...raises: [], tags: [].}: Source Edit
proc `not`(x: JsObject): JsObject {.importjs: "(!#)", ...raises: [], tags: [].}: Source Edit
proc `or`(x, y: JsObject): JsObject {.importjs: "(# || #)", ...raises: [], tags: [].}: Source Edit
proc hasOwnProperty(x: JsObject; prop: cstring): bool {. importjs: "#.hasOwnProperty(#)", ...raises: [], tags: [].}: Checks, whether x has a property of name prop. Source Edit
proc isNull[T](x: T): bool {.noSideEffect, importjs: "(# === null)", ...raises: [], tags: [].}: Checks if a value is exactly null. Source Edit
proc isUndefined[T](x: T): bool {.noSideEffect, importjs: "(# === undefined)", ...raises: [], tags: [].}: Checks if a value is exactly undefined. Source Edit
proc jsDelete(x: auto): JsObject {.importjs: "(delete #)", ...raises: [], tags: [].}: JavaScript's delete operator. Source Edit
proc jsNew(x: auto): JsObject {.importjs: "(new #)", ...raises: [], tags: [].}: Turns a regular function call into an invocation of the JavaScript's new operator. Source Edit
proc jsTypeOf(x: JsObject): cstring {.importjs: "typeof(#)", ...raises: [], tags: [].}: Returns the name of the JsObject's JavaScript type as a cstring. Source Edit
proc newJsAssoc[K: JsKey; V](): JsAssoc[K, V] {.importjs: "{@}", ...raises: [], tags: [].}: Creates a new empty JsAssoc with key type K and value type V. Source Edit
proc newJsObject(): JsObject {.importjs: "{@}", ...raises: [], tags: [].}: Creates a new empty JsObject. Source Edit
proc require(module: cstring): JsObject {.importc, ...raises: [], tags: [].}: JavaScript's require function. Source Edit
proc to(x: JsObject; T: typedesc): T:type {.importjs: "(#)", ...raises: [], tags: [].}: Converts a JsObject x to type T. Source Edit
proc toJs[T](val: T): JsObject {.importjs: "(#)", ...raises: [], tags: [].}: Converts a value of any type to type JsObject. Source Edit
proc toJsKey(text: cstring; t: type cstring): cstring: Source Edit
proc toJsKey[T: enum](text: cstring; t: type T): T: Source Edit
proc toJsKey[T: SomeFloat](text: cstring; t: type T): T {. importjs: "parseFloat(#)", ...raises: [], tags: [].}: Source Edit
proc toJsKey[T: SomeInteger](text: cstring; t: type T): T {. importjs: "parseInt(#)", ...raises: [], tags: [].}: Source Edit

Iterators

iterator items(obj: JsObject): JsObject {....raises: [], tags: [].}: Yields the values of each field in a JsObject, wrapped into a JsObject. Source Edit
iterator items[K, V](assoc: JsAssoc[K, V]): V: Yields the values in a JsAssoc. Source Edit
iterator keys(obj: JsObject): cstring {....raises: [], tags: [].}: Yields the names of each field in a JsObject. Source Edit
iterator keys[K: JsKey; V](assoc: JsAssoc[K, V]): K: Yields the keys in a JsAssoc. Source Edit
iterator pairs(obj: JsObject): (cstring, JsObject) {....raises: [], tags: [].}: Yields tuples of type (cstring, JsObject), with the first entry being the name of a fields in the JsObject and the second being its value wrapped into a JsObject. Source Edit
iterator pairs[K: JsKey; V](assoc: JsAssoc[K, V]): (K, V): Yields tuples of type (K, V), with the first entry being a key in the JsAssoc and the second being its corresponding value. Source Edit

Macros

macro `.()`(obj: JsObject; field: untyped; args: varargs[JsObject, jsFromAst]): JsObject

Experimental "method call" operator for type JsObject. Takes the name of a method of the JavaScript object (field) and calls it with args as arguments, returning a JsObject (which may be discarded, and may be undefined, if the method does not return anything, so be careful when using this.)

Example:

# Let's get back to the console example:
var console {.importc, nodecl.}: JsObject
let res = console.log("I return undefined!")
console.log(res) # This prints undefined, as console.log always returns
                 # undefined. Thus one has to be careful, when using
                 # JsObject calls.

Source Edit

macro `.()`[K: cstring; V: proc](obj: JsAssoc[K, V]; field: untyped;
                                 args: varargs[untyped]): auto

Experimental "method call" operator for type JsAssoc. Takes the name of a method of the JavaScript object (field) and calls it with args as arguments. Here, everything is typechecked, so you do not have to worry about undefined return values. Source Edit

macro `.=`(obj: JsObject; field, value: untyped): untyped

Experimental dot accessor (set) for type JsObject. Sets the value of a property of name field in a JsObject x to value. Source Edit

macro `.=`[K: cstring; V](obj: JsAssoc[K, V]; field: untyped; value: V): untyped

Experimental dot accessor (set) for type JsAssoc. Sets the value of a property of name field in a JsObject x to value. Source Edit

macro `.`(obj: JsObject; field: untyped): JsObject

Experimental dot accessor (get) for type JsObject. Returns the value of a property of name field from a JsObject x.

Example:

let obj = newJsObject()
obj.a = 20
assert obj.a.to(int) == 20

Source Edit

macro `.`[K: cstring; V](obj: JsAssoc[K, V]; field: untyped): V

Experimental dot accessor (get) for type JsAssoc. Returns the value of a property of name field from a JsObject x. Source Edit

macro `{}`(typ: typedesc; xs: varargs[untyped]): auto

Takes a typedesc as its first argument, and a series of expressions of type key: value, and returns a value of the specified type with each field key set to value, as specified in the arguments of {}.

Example:

# Let's say we have a type with a ton of fields, where some fields do not
# need to be set, and we do not want those fields to be set to `nil`:
type
  ExtremelyHugeType = ref object
    a, b, c, d, e, f, g: int
    h, i, j, k, l: cstring
    # And even more fields ...

let obj = ExtremelyHugeType{ a: 1, k: "foo".cstring, d: 42 }

# This generates roughly the same JavaScript as:
{.emit: "var obj = {a: 1, k: "foo", d: 42};".}

Source Edit

macro bindMethod(procedure: typed): auto

Takes the name of a procedure and wraps it into a lambda missing the first argument, which passes the JavaScript builtin this as the first argument to the procedure. Returns the resulting lambda.

Example:

We want to generate roughly this JavaScript:

var obj = {a: 10};
obj.someMethod = function() {
  return this.a + 42;
};

We can achieve this using the bindMethod macro:

let obj = JsObject{ a: 10 }
proc someMethodImpl(that: JsObject): int =
  that.a.to(int) + 42
obj.someMethod = bindMethod someMethodImpl

# Alternatively:
obj.someMethod = bindMethod
  proc(that: JsObject): int = that.a.to(int) + 42

Source Edit

macro jsFromAst(n: untyped): untyped

Source Edit

Templates

template toJs(s: string): JsObject: Source Edit