Logging variable in nodejs

Question

I have a variable named, 'res'. This variable if used with console.log() print all request to a function. My question is... How to log this variable in a log.txt file?

Example using console.log(res)

Print in console:

[ 'AndroidShareANE',
  'pixi.js',
  'ShortSword',
  'faceshiftparser',
  'clmutils',
  'chaikin-smooth',
  'getuservideo',
  'getboundingbox',
  'clmdraw',
  'SpriteSheetScrubberTutorial',
  'interpolation-arrays',

This is a one part of response.

My purpose is log in log.txt file the var content. Identical to console.log() result.

Thanks for your collaboration, and sorry my bad english.

'var' is a reserved word. You shouldn't use it as a variable name. — PeterVC, Dec 07 '16 at 19:34
this question may be duplicated: http://stackoverflow.com/questions/8393636/node-log-in-a-file-instead-of-the-console — Yumarx Polanco, Dec 07 '16 at 19:46

score 2 · Accepted Answer · answered Dec 07 '16 at 19:34

2

The easiest way is to create a new Console object that writes to your file. The docs have an example of this exact thing, which I'll reproduce here for posterity:

const output = fs.createWriteStream('./stdout.log');
const errorOutput = fs.createWriteStream('./stderr.log');
// custom simple logger
const logger = new Console(output, errorOutput);
// use it like console
var count = 5;
logger.log('count: %d', count);
// in stdout.log: count 5

If you don't pass the second argument (errorOutput) to new Console then the error output will also be written to the output file.

answered Dec 07 '16 at 19:34

Jordan Running

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Mhm, and my variable 'var' containing result, where is located? – Santiago D'Antuoni Dec 07 '16 at 19:43
In the above code `logger` is an instance of Console, just like `console` in `console.log`. You give your variable as an argument to `logger.log`, just like you did with `console.log`. – Jordan Running Dec 07 '16 at 19:44
Please, give me a example for this. – Santiago D'Antuoni Dec 07 '16 at 19:52
`logger.log(var)`. – Jordan Running Dec 07 '16 at 19:52
See "ReferenceError: Console is not defined" error. – Santiago D'Antuoni Dec 07 '16 at 19:56
You need to `require('console')` (and assign it to a variable named `Console`) just like any other Node.js module. – Jordan Running Dec 07 '16 at 19:59
TypeError: Console is not a constructor – Santiago D'Antuoni Dec 07 '16 at 20:15
Looking more closely at the docs, the Console constructor is a property of the `console` module, so you'll want to do e.g. `const Console = require('console').Console`. – Jordan Running Dec 07 '16 at 20:23

Logging variable in nodejs

1 Answers1