Reputation: 1846
I am working on a game using NodeJs, and realized it would be immensly helpful to have access to old console.log
output. The mechanics and calculations get rather complicated, and it would be nice to have access to them later to search through and do some data analysis on them to find the correct values for my modifiers (battle mechanics). At the same time, I want to see console.log
in the console as well.
I know this isn't possible with regular javascript, (see This), but I was hoping npm had a package of some way to intercept logs and log them to a file on the server. Any thoughts?
Upvotes: 4
Views: 6019
Reputation: 73928
The purest form would be by overriding stdout
and stderr
methods, e.g.
process.stdout.write = (data) => {
w(data);
};
process.stderr.write = (data) => {
w(data);
};
Here w
is whatever mechanism that you would like to use to record this data, e.g.
const w = (...args) => {
appendFileSync(
path.resolve(__dirname, "test.json"),
JSON.stringify(args, null, " ")
);
};
Beware that you cannot output anything from this function as that would cause an infinite loop.
The above behaviour would discard any output though. If you want the program to continue producing output, then you need to call the original write
methods, e.g.
const stdoutWrite = process.stdout.write.bind(process.stdout);
const stderrWrite = process.stderr.write.bind(process.stderr);
process.stdout.write = (data, callback) => {
w(data);
return stdoutWrite(data, callback);
};
process.stderr.write = (data, callback) => {
w(data);
return stderrWrite(data, callback);
};
Upvotes: 2
Reputation: 397
An NPM option to log to stdout and to a file at the same time could be Winston. Winston is a logging library that allows you to define your own loggers, specifying their transports (a transport being what do you do with these log lines). In your case, you could define a logger with two transports, stdout and a log file. Example (inspired by the Winston documentation):
const winston = require('winston');
let logger = new (winston.Logger)({
transports: [
new (winston.transports.Console)(),
new (winston.transports.File)({ filename: 'somefile.log' })
]
});
logger.info('hello, world!');
If you run this code above, you'll see the logs in the console and in somefile.log
.
Upvotes: 8
Reputation: 3483
You can intercept console.log like so
var cl = console.log
console.log = function(...args){
// your custom logging logic here
cl.apply(console, args)
}
Upvotes: 14