| Type: | Package |
| Title: | Tools for Working with JavaScript in R |
| Version: | 1.2.1 |
| Description: | A set of utilities for working with JavaScript syntax in R. Includes tools to parse, tokenize, compile, validate, reformat, optimize and analyze JavaScript code. |
| License: | MIT + file LICENSE |
| URL: | https://jeroen.r-universe.dev/js |
| BugReports: | https://github.com/jeroen/js/issues |
| VignetteBuilder: | knitr |
| Imports: | V8 (≥ 0.5) |
| Suggests: | knitr, rmarkdown |
| RoxygenNote: | 6.0.1 |
| NeedsCompilation: | no |
| Packaged: | 2024-10-03 14:12:57 UTC; jeroen |
| Author: | Jeroen Ooms  [aut,
cre] |
| Maintainer: | Jeroen Ooms <jeroenooms@gmail.com> |
| Repository: | CRAN |
| Date/Publication: | 2024-10-04 12:10:02 UTC |
Coffee Script
Description
Compiles coffee script into JavaScript.
Usage
coffee_compile(code, ...)
Arguments
code |
a string with JavaScript code |
... |
additional options passed to the compiler |
Examples
# Hello world
coffee_compile("square = (x) -> x * x")
coffee_compile("square = (x) -> x * x", bare = TRUE)
# Simple script
demo <- readLines(system.file("example/demo.coffee", package = "js"))
js <- coffee_compile(demo)
cat(js)
cat(uglify_optimize(js))
JavaScrip Syntax Tree
Description
Esprima is a high performance, standard-compliant ECMAScript parser. It has full support for ECMAScript 2017 and returns a sensible syntax tree format as standardized by ESTree project.
Usage
esprima_tokenize(text, range = FALSE, loc = FALSE, comment = FALSE)
esprima_parse(text, jsx = FALSE, range = FALSE, loc = FALSE,
tolerant = FALSE, tokens = FALSE, comment = FALSE)
Arguments
text |
a character vector with JavaScript code |
range |
Annotate each token with its zero-based start and end location |
loc |
Annotate each token with its column and row-based location |
comment |
Include every line and block comment in the output |
jsx |
Support JSX syntax |
tolerant |
Tolerate a few cases of syntax errors |
tokens |
Collect every token |
Details
The esprima_tokenize function returns a data frame with JavaScript tokens. The
esprima_parse function returns the Syntax Tree in JSON format. This can be parsed to R
using e.g. jsonlite::fromJSON.
References
Esprima documentation: http://esprima.readthedocs.io/en/4.0/.
Examples
code <- "function test(x, y){ x = x || 1; y = y || 1; return x*y;}"
esprima_tokenize(code)
esprima_parse(code)
Evaluate JavaScript
Description
Evaluate a piece of JavaScript code in a disposable context.
Usage
js_eval(text)
Arguments
text |
JavaScript code |
Examples
# Stateless evaluation
js_eval("(function() {return 'foo'})()")
# Use V8 for stateful evaluation
ct <- V8::new_context()
ct$eval("var foo = 123")
ct$get("foo")
Get the type of a JavaScript object
Description
JavaScript wrapper to typeof to test if a piece of JavaScript code is
syntactically valid, and the type of object it evaluates to. Useful to
verify that a piece of JavaScript code contains a proper function/object.
Usage
js_typeof(text)
Arguments
text |
JavaScript code |
Examples
js_typeof("function(x){return x+1}")
js_typeof("(function() {return 'foo'})()")
js_typeof("{foo : 123, bar : true}")
Validate JavaScript
Description
Simple wrapper for ct$validate in V8.
Tests if code constitutes a syntactically valid JS script.
Usage
js_validate_script(text, error = TRUE)
Arguments
text |
character vector with JavaScript code |
error |
raise error on invalid code |
Examples
js_validate_script("function foo(x){2*x}") #TRUE
js_validate_script("foo = function(x){2*x}") #TRUE
# Anonymous functions in global scope are invalid
js_validate_script("function(x){2*x}", error = FALSE) #FALSE
# Use ! or () to check anonymous function syntax
js_validate_script("!function(x){2*x}") #TRUE
js_validate_script("(function(x){2*x})") #TRUE
Static analysis tool for JavaScript
Description
JSHint is a community-driven tool to detect errors and potential problems in JavaScript code. It is very flexible so you can easily adjust it to your particular coding guidelines and the environment you expect your code to execute in.
Usage
jshint(text, ..., globals = NULL)
Arguments
text |
a string of JavaScript code |
... |
additional jshint configuration options |
globals |
a white list of global variables that are not formally defined in the source code |
Value
a data frame where each row represents a jshint error or NULL if there were no errors
Examples
code = "var foo = 123"
jshint(code)
jshint(code, asi = TRUE)
Compress and Reformat JavaScript Code
Description
UglifyJS is a JavaScript compressor/minifier written in JavaScript. It also contains tools that allow one to automate working with JavaScript code.
Usage
uglify_reformat(text, beautify = FALSE, ...)
uglify_optimize(text, ...)
uglify_files(files, ...)
Arguments
text |
a character vector with JavaScript code |
beautify |
prettify (instead of minify) code |
files |
a character vector of filenames |
... |
References
UglifyJS2 Documentation: https://lisperator.net/uglifyjs/.
Examples
code <- "function test(x, y){ x = x || 1; y = y || 1; return x*y;}"
cat(uglify_optimize(code))
cat(uglify_reformat(code, beautify = TRUE, indent_level = 2))