What is this element readLines ? Is this the function readLines ?
I think the file path is in json_files[[i]] isn't it ?
Why do you try to use paste ?
jsonlite::fromJSON can read from a file. see ?jsonlite::fromJSON
You could manage to do it maybe with
json_data <- purrr::map(json_files, fromJSON)
See purrr for functional programming helpers.