replace int0 w na

library(httr)
library(jsonlite)
res <- GET("http://api.themoviedb.org/3/discover/movie?release_date.gte=2017-12-01&release_date.lte=2017-12-31&api_key=606aaffd7ca10f0b80804a1f0674e4e1&page=1") %>% 
  content("text") %>% 
  fromJSON()



int0_to_na <- function(x) {
  #https://stackoverflow.com/questions/21218041/replace-integer0-by-na
  if (length(x) == 0)
    return(NA)
  return(x)
}

res %>% 
  as_tibble() %>% 
  jsonlite::flatten() %>% 
  as_tibble() %>% 
  unnest() %>% 
  mutate(x = map_int(results.genre_ids, int0_to_na)) %>% 
  select(results.genre_ids, x)