Convert JavaScript array of objects to JSON in r programming language

Question

I need to pass JSON object to a function in r programming. The following are the various examples of JavaScript objects that can be passed which needed to be converted to JSON in r

Example1 = [
  {name: "Orange", data: {"Tuesday": 3, "Friday": 4}, stack: "fruit"},
  {name: "Apple", data: {"Tuesday": 1, "Friday": 8}, stack: "fruit"},
  {name: "Cucumber", data: {"Tuesday": 3, "Friday": 4}, stack: "vegetable"},
  {name: "Carrot", data: {"Tuesday": 1, "Friday": 8}, stack: "vegetable"}
]

Example2 = [["Washington", "1789-04-29", "1797-03-03"], ["Adams", "1797-03-03", "1801-03-03"]]

I need help converting them into a JSON object in r using jsonlite package.

Answer 1

To have a "true" JSON string, you can use the jsonNormalize package.

library(jsonNormalize)

jsonNormalize(
  '[
  {name: "Orange", data: {"Tuesday": 3, "Friday": 4}, stack: "fruit"},
  {name: "Apple", data: {"Tuesday": 1, "Friday": 8}, stack: "fruit"},
  {name: "Cucumber", data: {"Tuesday": 3, "Friday": 4}, stack: "vegetable"},
  {name: "Carrot", data: {"Tuesday": 1, "Friday": 8}, stack: "vegetable"}
]', prettify = TRUE)

[
  {
    "name": "Orange",
    "data": {
      "Tuesday": 3,
      "Friday": 4
    },
    "stack": "fruit"
  },
  {
    "name": "Apple",
    "data": {
      "Tuesday": 1,
      "Friday": 8
    },
    "stack": "fruit"
  },
  {
    "name": "Cucumber",
    "data": {
      "Tuesday": 3,
      "Friday": 4
    },
    "stack": "vegetable"
  },
  {
    "name": "Carrot",
    "data": {
      "Tuesday": 1,
      "Friday": 8
    },
    "stack": "vegetable"
  }
]

The jsonNormalize package also provides a RStudio addin allowing to normalize a json file by pressing a button.

Answer 2

Javascript code can be evaluated with v8, that code can include JSON.stringify(), but for a list of simple assignment expressions we can set serialize parameter for $eval() method and it will return JSON string:

library(V8)
#> Using V8 engine 9.1.269.38
js <- c(
  ex1 = 'Example1 = [
  {name: "Orange", data: {"Tuesday": 3, "Friday": 4}, stack: "fruit"},
  {name: "Apple", data: {"Tuesday": 1, "Friday": 8}, stack: "fruit"},
  {name: "Cucumber", data: {"Tuesday": 3, "Friday": 4}, stack: "vegetable"},
  {name: "Carrot", data: {"Tuesday": 1, "Friday": 8}, stack: "vegetable"}
]',
  ex2 = 'Example2 = [["Washington", "1789-04-29", "1797-03-03"], ["Adams", "1797-03-03", "1801-03-03"]]'
)

ctx <- v8()
# evaluate and serialize js return object
json_1 <- ctx$eval(js[1], serialize = TRUE) 
jsonlite::validate(json_1)
#> [1] TRUE
json_1
#> [1] "[{\"name\":\"Orange\",\"data\":{\"Tuesday\":3,\"Friday\":4},\"stack\":\"fruit\"},{\"name\":\"Apple\",\"data\":{\"Tuesday\":1,\"Friday\":8},\"stack\":\"fruit\"},{\"name\":\"Cucumber\",\"data\":{\"Tuesday\":3,\"Friday\":4},\"stack\":\"vegetable\"},{\"name\":\"Carrot\",\"data\":{\"Tuesday\":1,\"Friday\":8},\"stack\":\"vegetable\"}]"

# or apply ctx$eval() on the the list of expressions
json_lst <- lapply(js, ctx$eval, serialize = TRUE)
str(json_lst)
#> List of 2
#>  $ ex1: chr "[{\"name\":\"Orange\",\"data\":{\"Tuesday\":3,\"Friday\":4},\"stack\":\"fruit\"},{\"name\":\"Apple\",\"data\":{"| __truncated__
#>  $ ex2: chr "[[\"Washington\",\"1789-04-29\",\"1797-03-03\"],[\"Adams\",\"1797-03-03\",\"1801-03-03\"]]"

^{Created on 2023-07-23 with reprex v2.0.2}