append json objects to file with nodejs

Question

I simply want to write a json object into a file (not necessarily a .json file) after calling a certain function. When calling that function with another json object, I want to append that object to the file.

Currently I am using jsonfile for that.

var jsonfile = require('jsonfile');
...
users_file = "./users_file";
function update(user_json) {
    jsonfile.writeFile(users_file,user_json), function(err) {
        console.error(err);
    });
}

But calling update again with another json object, the first line will be overwritten.

example:

json1 = {"id":123456,"first_name":"John","last_name":"Smith","username":"johnsmith"}
json2 = {"id":654321,"first_name":"marc","last_name":"cold","username":"marccold"}

when calling update(json1) and later update(json2) I want the file to look like this:

{"id":123456,"first_name":"John","last_name":"Smith","username":"johnsmith"}
{"id":654321,"first_name":"marc","last_name":"cold","username":"marccold"}

Currently the second line is replacing the first line. I tried to read the file first and then concat both json objects but that failed. Also that needs to work when the file is empty.

Answer 1

Use appendFile() instead of writeFile(). writeFile() is to write a new file or overwrite existing file if any. While appendFile() is to append Content to the existing file if any or create a new file and add the content.