use V8 for a babel transform helper

Author: timelyportfolio

DESCRIPTION

@@ -24,5 +24,6 @@ Imports:
 Suggests:
     htmlwidgets (>= 0.6.0),
     rmarkdown,
-    shiny
+    shiny,
+    V8
 RoxygenNote: 5.0.1

NAMESPACE

@@ -1,4 +1,5 @@
 # Generated by roxygen2: do not edit by hand
 
+export(babel_transform)
 export(html_dependency_react)
 importFrom(htmltools,htmlDependency)

R/babel.R

@@ -0,0 +1,21 @@
+#' Transform Code with Babel
+#'
+#' Helper function to use \code{V8} with \code{Babel} so we can
+#' avoid a JSX transformer with using \code{reactR}.
+#'
+#' @param code \code{character}
+#'
+#' @return transformed \code{character}
+#' @export
+#'
+#' @examples
+#' library(reactR)
+#' babel_transform('<div>react div</div>')
+babel_transform <- function(code=""){
+  stopifnot(require(V8), is.character(code))
+
+  ctx <- v8()
+  ctx$source('https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.10.3/babel.min.js')
+  ctx$assign('code', code)
+  ctx$get('Babel.transform(code,{ presets: ["es2015","react"] }).code')
+}

README.md

@@ -1,6 +1,6 @@
 # reactR
 
-A convenience function with local dependencies for using [`React`](https://facebook.github.io/react) in `R`.  This is modeled after the `html_dependency_*` functions from RStudio's [`rmarkdown`](https://github.com/rstudio/rmarkdown) package.
+A set of convenience function with local dependencies for using [`React`](https://facebook.github.io/react) in `R`.  This is modeled after the `html_dependency_*` functions from RStudio's [`rmarkdown`](https://github.com/rstudio/rmarkdown) package.
 
 ## Installation
 
@@ -34,6 +34,22 @@ browsable(attachDependencies(
 ))
 ```
 
+`reactR` also uses `V8` if available to transform `JSX` and `ES2015` code.
+
+```R
+library(reactR)
+library(htmltools)
+
+browsable(
+  attachDependencies(
+    tags$script(
+      babel_transform('ReactDOM.render(<h1>Powered By React/JSX</h1>,document.body)')
+    ),
+    html_dependency_react()
+  )
+)
+```
+
 ## Contributing and Code of Conduct
 
 I welcome contributors.  Help make this package great.  Please note that this project is released with a [Contributor Code of Conduct](CONDUCT.md). By participating in this project you agree to abide by its terms.