Any way to write req object of callback route to a file in NodeJS?

Question

All I want is to log my req/res object to a file(so i can refer to it later for any object values) on redirecting to a particular page.

I tried this:

app.get("/route", function(req, res) {
res.render("route");
fs.writeFile('./data.json', JSON.stringify(req, null, 2) , 'utf-8', function(err) {
    if(err) {
        return console.log(err);
    }
    console.log("The file was saved!");
});

The above code is throwing error as so:

TypeError: Converting circular structure to JSON at Object.Stringify (native)

Is there anything I should be doing differently? Any help is appreciated. Thanks in advance.

Possible duplicate of [JSON.stringify, avoid TypeError: Converting circular structure to JSON](https://stackoverflow.com/questions/11616630/json-stringify-avoid-typeerror-converting-circular-structure-to-json) — Gian Marco Toso, Nov 09 '17 at 12:24
Why do you want to save the entire object? What fields do you want to store? — Tvde1, Nov 09 '17 at 12:25
Specifically for you case I'd consider this answer: https://stackoverflow.com/a/18354289/1053772 — Gian Marco Toso, Nov 09 '17 at 12:26
Thank @Almis , using util.inspect works for me as I'm trying to stringify an object which is circular structure and using util.inspect translates that into a [circular] object instead. — Vignesh Sharma, Nov 09 '17 at 13:31

score 0 · Answer 1 · answered Nov 09 '17 at 12:27

req contains a reference to the res object, and res contains a reference back to req, so it really is a circular reference where stringify will not work.

A quick solution might be to be more choosy about which properties you want to save. For example, save req.body to file - just be picky about the data you really need.

Long term, you should consider if this is what you really want. File I/O is "expensive". You might want to put data into a database, or keep it in memory somehow.

score 0 · Answer 2 · answered Nov 09 '17 at 12:32

Are you need all req-object to save?

If you should save only query, try this:

app.get("/route", function(req, res) {
     res.render("route");
     fs.writeFile('./data.json', JSON.stringify(req.query, null, 2), 
    'utf-8', function(err) {
         if(err) {
              return console.log(err);
         }
    console.log("The file was saved!");
 });

if you want any additional data, firstly create new object, and assign this data to that object, and use JSON.stringify(yourObject, null, 2)

Any way to write req object of callback route to a file in NodeJS?

2 Answers2