A simple JSON serializer

A JSON serializer that only works on a limited types of R data (NULL, lists, arrays, logical/character/numeric/date/time vectors). Other types of data will be coerced to character. A character string of the class JS_LITERAL is treated as raw JavaScript, so will not be quoted. The function json_vector() converts an atomic R vector to JSON.

tojson(x)

json_vector(x, to_array = FALSE, quote = TRUE)

Arguments

x

An R object.

to_array

Whether to convert a vector to a JSON array (use []).

quote

Whether to double quote the elements.

Value

A character string.

Details

Both NULL and NA are converted to null. Named lists are converted to objects of the form {key1: value1, key2: value2, ...}. Unnamed lists are converted to arrays of the form [[value1], [value2], ...]. The same rules apply to data frames since technically they are also lists. However, please note that unnamed data frames (i.e., without column names) will be converted to an array with each row as an array element, whereas named data frames will have each column as an individual element. For matrices, the JSON array will have each row as an individual element, and names are discarded.

Dates and times are coerced to character using UTC as the timezone, and represented via the JavaScript expression new Date(value) (which is not standard JSON but practically more useful).

See also

The jsonlite package provides a full JSON serializer.

Examples

library(xfun)
tojson(NULL)
#> null
tojson(1:10)
#> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
tojson(TRUE)
#> true
tojson(FALSE)
#> false
tojson(list(a = 1, b = list(c = 1:3, d = "abc")))
#> {
#>   "a": 1,
#>   "b": {
#>     "c": [1, 2, 3],
#>     "d": "abc"
#>   }
#> }
tojson(list(c("a", "b"), 1:5, TRUE, Sys.Date() + 1:3))
#> [
#>   ["a", "b"],
#>   [1, 2, 3, 4, 5],
#>   true,
#>   [new Date("2025-11-19"), new Date("2025-11-20"), new Date("2025-11-21")]
#> ]
tojson(head(iris))  # each column is in an element
#> {
#>   "Sepal.Length": [5.1, 4.9, 4.7, 4.6, 5, 5.4],
#>   "Sepal.Width": [3.5, 3, 3.2, 3.1, 3.6, 3.9],
#>   "Petal.Length": [1.4, 1.4, 1.3, 1.5, 1.4, 1.7],
#>   "Petal.Width": [0.2, 0.2, 0.2, 0.2, 0.2, 0.4],
#>   "Species": ["setosa", "setosa", "setosa", "setosa", "setosa", "setosa"]
#> }
tojson(unname(head(iris)))  # each row is in an element
#> [
#>   [5.1, 3.5, 1.4, 0.2, "setosa"],
#>   [4.9, 3, 1.4, 0.2, "setosa"],
#>   [4.7, 3.2, 1.3, 0.2, "setosa"],
#>   [4.6, 3.1, 1.5, 0.2, "setosa"],
#>   [5, 3.6, 1.4, 0.2, "setosa"],
#>   [5.4, 3.9, 1.7, 0.4, "setosa"]
#> ]
tojson(matrix(1:12, 3))
#> [
#>   [1, 4, 7, 10],
#>   [2, 5, 8, 11],
#>   [3, 6, 9, 12]
#> ]

# literal JS code
JS = function(x) structure(x, class = "JS_LITERAL")
tojson(list(a = 1:5, b = JS("function() {return true;}")))
#> {
#>   "a": [1, 2, 3, 4, 5],
#>   "b": function() {return true;}
#> }