std/jsffi
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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
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JsAssoc[K; V] = ref object of JsRoot
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Statically typed wrapper around a JavaScript object. Source Edit
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JsError {.importc: "Error".} = object of JsRoot
message*: cstring
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JsEvalError {.importc: "EvalError".} = object of JsError
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JsKey = concept atypeof(T)
cstring.toJsKey(T) is T
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JsObject = ref object of JsRoot
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Dynamically typed wrapper around a JavaScript object. Source Edit
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JsRangeError {.importc: "RangeError".} = object of JsError
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JsReferenceError {.importc: "ReferenceError".} = object of JsError
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JsSyntaxError {.importc: "SyntaxError".} = object of JsError
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JsTypeError {.importc: "TypeError".} = object of JsError
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JsURIError {.importc: "URIError".} = object of JsError
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Vars
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jsArguments {.importc: "arguments", nodecl.}: JsObject
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JavaScript's arguments pseudo-variable. Source Edit
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jsDirname {.importc: "__dirname", nodecl.}: cstring
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JavaScript's __dirname pseudo-variable. Source Edit
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jsFilename {.importc: "__filename", nodecl.}: cstring
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JavaScript's __filename pseudo-variable. Source Edit
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jsNull {.importc: "null", nodecl.}: JsObject
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JavaScript's null literal. Source Edit
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jsUndefined {.importc: "undefined", nodecl.}: JsObject
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JavaScript's undefined literal. Source Edit
Procs
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proc `%`(x, y: JsObject): JsObject {.importjs: "(# % #)", ...raises: [], tags: [],
forbids: [].}
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proc `%=`(x, y: JsObject): JsObject {.importjs: "(# %= #)", discardable,
...raises: [], tags: [], forbids: [].}
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proc `&`(a, b: cstring): cstring {.importjs: "(# + #)", ...raises: [], tags: [],
forbids: [].}
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Concatenation operator for JavaScript strings. Source Edit
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proc `*`(x, y: JsObject): JsObject {.importjs: "(# * #)", ...raises: [], tags: [],
forbids: [].}
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proc `**`(x, y: JsObject): JsObject {.importjs: "((#) ** #)", ...raises: [],
tags: [], forbids: [].}
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proc `*=`(x, y: JsObject): JsObject {.importjs: "(# *= #)", discardable,
...raises: [], tags: [], forbids: [].}
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proc `+`(x, y: JsObject): JsObject {.importjs: "(# + #)", ...raises: [], tags: [],
forbids: [].}
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proc `++`(x: JsObject): JsObject {.importjs: "(++#)", ...raises: [], tags: [],
forbids: [].}
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proc `+=`(x, y: JsObject): JsObject {.importjs: "(# += #)", discardable,
...raises: [], tags: [], forbids: [].}
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proc `-`(x, y: JsObject): JsObject {.importjs: "(# - #)", ...raises: [], tags: [],
forbids: [].}
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proc `--`(x: JsObject): JsObject {.importjs: "(--#)", ...raises: [], tags: [],
forbids: [].}
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proc `-=`(x, y: JsObject): JsObject {.importjs: "(# -= #)", discardable,
...raises: [], tags: [], forbids: [].}
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proc `/`(x, y: JsObject): JsObject {.importjs: "(# / #)", ...raises: [], tags: [],
forbids: [].}
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proc `/=`(x, y: JsObject): JsObject {.importjs: "(# /= #)", discardable,
...raises: [], tags: [], forbids: [].}
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proc `<`(x, y: JsObject): JsObject {.importjs: "(# < #)", ...raises: [], tags: [],
forbids: [].}
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proc `<=`(x, y: JsObject): JsObject {.importjs: "(# <= #)", ...raises: [],
tags: [], forbids: [].}
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proc `==`(x, y: JsRoot): bool {.importjs: "(# === #)", ...raises: [], tags: [],
forbids: [].}
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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
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proc `>`(x, y: JsObject): JsObject {.importjs: "(# > #)", ...raises: [], tags: [],
forbids: [].}
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proc `>=`(x, y: JsObject): JsObject {.importjs: "(# >= #)", ...raises: [],
tags: [], forbids: [].}
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proc `[]`(obj: JsObject; field: cstring): JsObject {.importjs: "#[#]",
...raises: [], tags: [], forbids: [].}
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Returns the value of a property of name
field from a JsObject obj. Source Edit
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proc `[]`(obj: JsObject; field: int): JsObject {.importjs: "#[#]", ...raises: [],
tags: [], forbids: [].}
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Returns the value of a property of name
field from a JsObject obj. Source Edit
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proc `[]`[K: JsKey; V](obj: JsAssoc[K, V]; field: K): V {.importjs: "#[#]",
...raises: [], tags: [], forbids: [].}
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Returns the value of a property of name
field from a JsAssoc obj. Source Edit
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proc `[]`[V](obj: JsAssoc[cstring, V]; field: string): V
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proc `[]=`[K: JsKey; V](obj: JsAssoc[K, V]; field: K; val: V) {.
importjs: "#[#] = #", ...raises: [], tags: [], forbids: [].}
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Sets the value of a property of name
field in a JsAssoc obj to v. Source Edit
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proc `[]=`[T](obj: JsObject; field: cstring; val: T) {.importjs: "#[#] = #",
...raises: [], tags: [], forbids: [].}
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Sets the value of a property of name
field in a JsObject obj to v. Source Edit
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proc `[]=`[T](obj: JsObject; field: int; val: T) {.importjs: "#[#] = #",
...raises: [], tags: [], forbids: [].}
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Sets the value of a property of name
field in a JsObject obj to v. Source Edit
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proc `[]=`[V](obj: JsAssoc[cstring, V]; field: string; val: V)
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proc `and`(x, y: JsObject): JsObject {.importjs: "(# && #)", ...raises: [],
tags: [], forbids: [].}
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proc hasOwnProperty(x: JsObject; prop: cstring): bool {.
importjs: "#.hasOwnProperty(#)", ...raises: [], tags: [], forbids: [].}
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Checks, whether
x has a property of name prop. Source Edit
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proc `in`(x, y: JsObject): JsObject {.importjs: "(# in #)", ...raises: [],
tags: [], forbids: [].}
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proc isNull[T](x: T): bool {.noSideEffect, importjs: "(# === null)", ...raises: [],
tags: [], forbids: [].}
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Checks if a value is exactly null. Source Edit
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proc isUndefined[T](x: T): bool {.noSideEffect, importjs: "(# === undefined)",
...raises: [], tags: [], forbids: [].}
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Checks if a value is exactly undefined. Source Edit
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proc jsDelete(x: auto): JsObject {.importjs: "(delete #)", ...raises: [], tags: [],
forbids: [].}
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JavaScript's
delete operator. Source Edit
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proc jsNew(x: auto): JsObject {.importjs: "(new #)", ...raises: [], tags: [],
forbids: [].}
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Turns a regular function call into an invocation of the JavaScript's
new operator. Source Edit
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proc jsTypeOf(x: JsObject): cstring {.importjs: "typeof(#)", ...raises: [],
tags: [], forbids: [].}
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Returns the name of the JsObject's JavaScript type as a cstring. Source Edit
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proc newJsAssoc[K: JsKey; V](): JsAssoc[K, V] {.importjs: "{@}", ...raises: [],
tags: [], forbids: [].}
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Creates a new empty JsAssoc with key type
K and value type V. Source Edit
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proc newJsObject(): JsObject {.importjs: "{@}", ...raises: [], tags: [],
forbids: [].}
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Creates a new empty JsObject. Source Edit
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proc `not`(x: JsObject): JsObject {.importjs: "(!#)", ...raises: [], tags: [],
forbids: [].}
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proc `or`(x, y: JsObject): JsObject {.importjs: "(# || #)", ...raises: [],
tags: [], forbids: [].}
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proc require(module: cstring): JsObject {.importc, ...raises: [], tags: [],
forbids: [].}
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JavaScript's
require function. Source Edit
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proc to(x: JsObject; T: typedesc): T:type {.importjs: "(#)", ...raises: [],
tags: [], forbids: [].}
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Converts a JsObject
x to type T. Source Edit
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proc toJs[T](val: T): JsObject {.importjs: "(#)", ...raises: [], tags: [],
forbids: [].}
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Converts a value of any type to type JsObject. Source Edit
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proc toJsKey(text: cstring; t: type cstring): cstring
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proc toJsKey[T: enum](text: cstring; t: type T): T
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proc toJsKey[T: SomeFloat](text: cstring; t: type T): T {.
importjs: "parseFloat(#)", ...raises: [], tags: [], forbids: [].}
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proc toJsKey[T: SomeInteger](text: cstring; t: type T): T {.
importjs: "parseInt(#)", ...raises: [], tags: [], forbids: [].}
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Iterators
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iterator items(obj: JsObject): JsObject {....raises: [], tags: [], forbids: [].}
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Yields the
values of each field in a JsObject, wrapped into a JsObject. Source Edit
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iterator items[K, V](assoc: JsAssoc[K, V]): V
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Yields the
values in a JsAssoc. Source Edit
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iterator keys(obj: JsObject): cstring {....raises: [], tags: [], forbids: [].}
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Yields the
names of each field in a JsObject. Source Edit
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iterator keys[K: JsKey; V](assoc: JsAssoc[K, V]): K
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Yields the
keys in a JsAssoc. Source Edit
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iterator pairs(obj: JsObject): (cstring, JsObject) {....raises: [], tags: [],
forbids: [].}
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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
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iterator pairs[K: JsKey; V](assoc: JsAssoc[K, V]): (K, V)
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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
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macro `.`(obj: JsObject; field: untyped): JsObject
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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
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macro `.`[K: cstring; V](obj: JsAssoc[K, V]; field: untyped): V
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Experimental dot accessor (get) for type JsAssoc. Returns the value of a property of name
field from a JsObject x. Source Edit
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macro `.()`(obj: JsObject; field: untyped; args: varargs[JsObject, jsFromAst]): JsObject
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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.
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macro `.()`[K: cstring; V: proc](obj: JsAssoc[K, V]; field: untyped;
args: varargs[untyped]): auto
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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
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macro `.=`(obj: JsObject; field, value: untyped): untyped
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Experimental dot accessor (set) for type JsObject. Sets the value of a property of name
field in a JsObject x to value. Source Edit
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macro `.=`[K: cstring; V](obj: JsAssoc[K, V]; field: untyped; value: V): untyped
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Experimental dot accessor (set) for type JsAssoc. Sets the value of a property of name
field in a JsObject x to value. Source Edit
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macro bindMethod(procedure: typed): auto
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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
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macro `{}`(typ: typedesc; xs: varargs[untyped]): auto
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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};".}
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