Handling milliseconds in POSIXct datetimes

[statquant]

Hello, thank you for this package I'm amazed at how fast it is.
I was trying to use it as a drop in replacement for jsonlite::toJSON to write data to be passed to a graphic library.
I noticed that I cannot get the milliseconds to "print" using yyjsonr as depicted in the following:

library(jsonlite)
library(yyjsonr)
library(data.table)

set.seed(1L)
options(digits.secs = 3)
N <- 10
DF <- data.table(
  date = Sys.Date() + seq_len(N),
  time_msec = as.POSIXct(Sys.Date()) + seq_len(N)/1e3,
  values = rnorm(N)
)
DF
#           date               time_msec     values
#         <Date>                  <POSc>      <num>
#  1: 2024-09-05 2024-09-04 00:00:00.000 -0.6264538
#  2: 2024-09-06 2024-09-04 00:00:00.002  0.1836433
#  3: 2024-09-07 2024-09-04 00:00:00.003 -0.8356286
#  4: 2024-09-08 2024-09-04 00:00:00.003  1.5952808
#  5: 2024-09-09 2024-09-04 00:00:00.005  0.3295078
#  6: 2024-09-10 2024-09-04 00:00:00.006 -0.8204684
#  7: 2024-09-11 2024-09-04 00:00:00.006  0.4874291
#  8: 2024-09-12 2024-09-04 00:00:00.007  0.7383247
#  9: 2024-09-13 2024-09-04 00:00:00.009  0.5757814
# 10: 2024-09-14 2024-09-04 00:00:00.009 -0.3053884

# Default jsonlite::toJSON 
jsonlite::toJSON(DF, digits = 4L)
# [{"date":"2024-09-05","time_msec":"2024-09-04 00:00:00.000","values":-0.6265},{"date":"2024-09-06","time_msec":"2024-09-04 00:00:00.002","values":0.1836},{"date":"2024-09-07","time_msec":"2024-09-04 00:00:00.003","values":-0.8356},{"date":"2024-09-08","time_msec":"2024-09-04 00:00:00.003","values":1.5953},{"date":"2024-09-09","time_msec":"2024-09-04 00:00:00.005","values":0.3295},{"date":"2024-09-10","time_msec":"2024-09-04 00:00:00.006","values":-0.8205},{"date":"2024-09-11","time_msec":"2024-09-04 00:00:00.006","values":0.4874},{"date":"2024-09-12","time_msec":"2024-09-04 00:00:00.007","values":0.7383},{"date":"2024-09-13","time_msec":"2024-09-04 00:00:00.009","values":0.5758},{"date":"2024-09-14","time_msec":"2024-09-04 00:00:00.009","values":-0.3054}] 

yyjsonr::write_json_str(DF, opts = list(digits = 4L))
# [1] "[{\"date\":\"2024-09-05\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":-0.6265},{\"date\":\"2024-09-06\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":0.1836},{\"date\":\"2024-09-07\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":-0.8356},{\"date\":\"2024-09-08\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":1.5953},{\"date\":\"2024-09-09\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":0.3295},{\"date\":\"2024-09-10\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":-0.8205},{\"date\":\"2024-09-11\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":0.4874},{\"date\":\"2024-09-12\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":0.7383},{\"date\":\"2024-09-13\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":0.5758},{\"date\":\"2024-09-14\",\"time_msec\":\"2024-09-04 00:00:00\",\"values\":-0.3054}]"

Sorry if that's obvious, is there something I can do to get the millis to show ?