Interface for the 'QuickJS' Lightweight 'JavaScript' Engine.
QuickJSR
A portable, lightweight, zero-dependency JavaScript engine for R, using QuickJS.
Values and objects are directly passed between R and QuickJS, with no need for serialization or deserialization. This both reduces overhead and allows for more complex data structures to be passed between R and JavaScript - including functions.
Installation
You can install the development version of QuickJSR from GitHub with:
# install.packages("remotes")
remotes::install_github("andrjohns/QuickJSR")
Or you can install pre-built binaries from R-Universe:
install.packages("QuickJSR", repos = c("https://andrjohns.r-universe.dev",
"https://cran.r-project.org"))
Usage
For standalone or simple JavaScript code, you can use the qjs_eval()
function:
library(QuickJSR)
qjs_eval("1 + 1")
#> [1] 2
qjs_eval("Math.random()")
#> [1] 0.5193045
For more complex interactions, you can create a QuickJS context and evaluate code within that context:
ctx <- JSContext$new()
Use the $source()
method to load JavaScript code into the context:
# Code can be provided as a string
ctx$source(code = "function add(a, b) { return a + b; }")
# Or read from a file
subtract_js <- tempfile(fileext = ".js")
writeLines("function subtract(a, b) { return a - b; }", subtract_js)
ctx$source(file = subtract_js)
Then use the $call()
method to call a specified function with arguments:
ctx$call("add", 1, 2)
#> [1] 3
ctx$call("subtract", 5, 3)
#> [1] 2
Interacting with R objects, environments, and functions
As QuickJSR uses the respective C APIs of R and QuickJS to pass values between the two, this allows for more complex data structures to be passed between R and JavaScript.
For example, you can also pass R functions to be evaluated using JavaScript arguments:
ctx$source(code = "function callRFunction(f, x, y) { return f(x, y); }")
ctx$call("callRFunction", function(x, y) x + y, 1, 2)
#> [1] 3
ctx$call("callRFunction", function(x, y) paste0(x, ",", y), "a", "b")
#> [1] "a,b"
You can pass R environments to JavaScript, and both access and update their contents:
env <- new.env()
env$x <- 1
env$y <- 2
ctx$source(code = "function accessEnv(env) { return env.x + env.y; }")
ctx$call("accessEnv", env)
#> [1] 3
ctx$source(code = "function updateEnv(env) { env.z = env.x * env.y; return env.z;}")
ctx$call("updateEnv", env)
#> [1] 2
env$z
#> [1] 2
QuickJSR also provides a global R
object, which you can use to access objects and functions from various R packages:
qjs_eval('R.package("base")["Sys.Date"]()')
#> [1] "2024-06-07 03:00:00 EEST"