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README.Rmd
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---
output: github_document
---
<!-- README.md is generated from README.Rmd. Please edit that file -->
```{r, include = FALSE}
knitr::opts_chunk$set(
collapse = TRUE,
comment = "#>",
fig.path = "man/figures/README-",
out.width = "100%"
)
```
# QuickJSR
<!-- badges: start -->
[](https://github.com/andrjohns/QuickJSR/actions/workflows/R-CMD-check.yaml)
[](https://CRAN.R-project.org/package=QuickJSR)
[](https://CRAN.R-project.org/package=QuickJSR)
[](https://andrjohns.r-universe.dev/QuickJSR)
<!-- badges: end -->
A portable, lightweight, zero-dependency JavaScript engine for R, using [QuickJS](https://bellard.org/quickjs/).
Values and objects are directly passed between R and QuickJS, with no need for serialization or deserialization. This both reduces overhead and allows for more complex data structures to be passed between R and JavaScript - including functions.
## Installation
You can install the development version of QuickJSR from [GitHub](https://github.com/) with:
```{r, eval=FALSE}
# install.packages("remotes")
remotes::install_github("andrjohns/QuickJSR")
```
Or you can install pre-built binaries from R-Universe:
```{r, eval=FALSE}
install.packages("QuickJSR", repos = c("https://andrjohns.r-universe.dev",
"https://cran.r-project.org"))
```
## Usage
For standalone or simple JavaScript code, you can use the `qjs_eval()` function:
```{r}
library(QuickJSR)
qjs_eval("1 + 1")
qjs_eval("Math.random()")
```
For more complex interactions, you can create a QuickJS context and evaluate code within that context:
```{r}
ctx <- JSContext$new()
```
Use the `$source()` method to load JavaScript code into the context:
```{r}
# Code can be provided as a string
ctx$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:
```{r}
ctx$call("add", 1, 2)
ctx$call("subtract", 5, 3)
```
### 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:
```{r}
ctx$source(code = "function callRFunction(f, x, y) { return f(x, y); }")
ctx$call("callRFunction", function(x, y) x + y, 1, 2)
ctx$call("callRFunction", function(x, y) paste0(x, ",", y), "a", "b")
```
You can pass R environments to JavaScript, and both access and update their contents:
```{r}
env <- new.env()
env$x <- 1
env$y <- 2
ctx$source(code = "function accessEnv(env) { return env.x + env.y; }")
ctx$call("accessEnv", env)
ctx$source(code = "function updateEnv(env) { env.z = env.x * env.y; return env.z;}")
ctx$call("updateEnv", env)
env$z
```
QuickJSR also provides a global `R` object, which you can use to access objects and functions from various R packages:
```{r}
qjs_eval('R.package("base")["Sys.Date"]()')
```