R call javascript

今天看到javascript call R似乎很容易

就稍微看一下R call javascript的方法

然後就看到V8這個套件，玩了一下覺得很驚豔XD

感覺javascript很適合拿來做一些R不容易做的功能XDD

library(V8)
ctx <- v8()
ctx$source("http://underscorejs.org/underscore-min.js")
ctx$eval("var list = [[0, 1], [2, 3], [4, 5]];")
ctx$eval("var flat = _.reduceRight(list, function(a, b) { return a.concat(b); }, []);")
ctx$get("flat")
# [1] 4 5 2 3 0 1

ctx$assign("x", 1:5)
ctx$eval("var y = _.each(x, function(x){ return x*3;})")
ctx$get("y")
# [1] 1 2 3 4 5

x2 <- 1:5
ctx$call("_.each", x2, JS("function(x){ return x*3;}"))
# [1] 1 2 3 4 5


ctx$call("_.filter", mtcars, JS("function(x){return x.mpg < 15}"))
#                      mpg cyl disp  hp drat    wt  qsec vs am gear carb
# Duster 360          14.3   8  360 245 3.21 3.570 15.84  0  0    3    4
# Cadillac Fleetwood  10.4   8  472 205 2.93 5.250 17.98  0  0    3    4
# Lincoln Continental 10.4   8  460 215 3.00 5.424 17.82  0  0    3    4
# Chrysler Imperial   14.7   8  440 230 3.23 5.345 17.42  0  0    3    4
# Camaro Z28          13.3   8  350 245 3.73 3.840 15.41  0  0    3    4

# work with npm
Sys.setenv(PATH = paste0(Sys.getenv("PATH"), ";C:\\Program Files\\nodejs;C:\\Users\\Jamal\\AppData\\Roaming\\npm"))
Sys.setenv(NODE_PATH = "C:\\Program Files\\nodejs\\node_modules;C:\\Users\\Jamal\\AppData\\Roaming\\npm\\node_modules")
system("npm install -g browserify js-beautify")
writeLines("global.beautify = require('js-beautify');", "in.js")
system("browserify in.js -o bundle.js")

ct <- v8()
ct$source("bundle.js")
test <- "(function(x,y){x = x || 1; y = y || 1; return y * x;})(4, 9)"
pretty_test <- ct$call("pr.js_beautify", test, list(indent_size = 2))
cat(pretty_test)
# (function(x, y) {
#   x = x || 1;
#   y = y || 1;
#   return y * x;
# })(4, 9)